ESP-IDF Component Continuous Integration (#229)

This pull request is meant to resolve #227 by adding continuous integration for publishing Libcanard to the [ESP Component Registry](https://components.espressif.com/).

Files added:
- `idf_component.yml`. This file contains required ESP component metadata.
- `Kconfig`. ESP components use this file as a standard way for controlling build options. I've added options for enabling/disabling assertions and the CRC table.
- `CMakeLists.txt`. This file is required to register the component with the ESP build system.
- `.github/workflows/esp_publish.yml`. This workflow uploads the component to the ESP-IDF registry whenever a new GitHub release is published.
- `.github/workflows/esp_dry_run.yml`. This workflow does a dry-run of uploading to the ESP-IDF registry, without publishing anything. It can only be manually triggered. I've tested this in my repository, and it seems to work.

The GitHub workflows require `IDF_COMPONENT_API_TOKEN` with an [ESP registry token](https://components.espressif.com/settings/tokens/) to be added to the repository secrets.

---------

Co-authored-by: Marcin Anforowicz <marcin.anforowicz@wibotic.com>
Co-authored-by: Pavel Kirienko <pavel.kirienko@gmail.com>

.github/workflows/esp_dry_run.yml

@@ -0,0 +1,22 @@
+# This workflow only runs when it is manually dispatched using GitHub.
+# It does a dry-run of publishing this project to the ESP component registry.
+# The project won't actually be published.
+
+name: Dry-run upload to the ESP component registry
+on:
+  workflow_dispatch:
+
+jobs:
+  upload_component:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          submodules: "recursive"
+
+      - name: Dry-run upload to the ESP component registry
+        run: |
+          bash esp_metadata/package_esp_component.sh
+          export IDF_COMPONENT_API_TOKEN="${{ secrets.IDF_COMPONENT_API_TOKEN }}"
+          cd package/libcanard
+          compote component upload --namespace opencyphal --name libcanard --version 0.0.0 --dry-run

.github/workflows/esp_publish.yml

@@ -0,0 +1,22 @@
+# This workflow gets triggered when a GitHub release is published.
+# It publishes this project to the public ESP-IDF component registry.
+
+name: Publish component to the ESP-IDF registry
+on:
+  release:
+    types: [published]
+
+jobs:
+  upload_component:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          submodules: "recursive"
+
+      - name: Publish component to the ESP-IDF registry
+        run: |
+          bash esp_metadata/package_esp_component.sh
+          export IDF_COMPONENT_API_TOKEN="${{ secrets.IDF_COMPONENT_API_TOKEN }}"
+          cd package/libcanard
+          compote component upload --namespace opencyphal --name libcanard --version ${{ github.event.release.tag_name }}

esp_metadata/CMakeLists.txt

@@ -0,0 +1,18 @@
+# This file is used when packaging libcanard
+# for the ESP-IDF component registry:
+# https://components.espressif.com/
+
+idf_component_register(SRCS "canard.c"
+                       INCLUDE_DIRS "include")
+
+# Apply the Kconfig options to the source file.
+
+if(NOT CONFIG_CANARD_ASSERTIONS)
+    target_compile_definitions(${COMPONENT_LIB} PRIVATE "CANARD_ASSERT=(void)")
+endif()
+
+if(CONFIG_CANARD_CRC_TABLE)
+    target_compile_definitions(${COMPONENT_LIB} PRIVATE CANARD_CRC_TABLE=1)
+else()
+    target_compile_definitions(${COMPONENT_LIB} PRIVATE CANARD_CRC_TABLE=0)
+endif()

esp_metadata/Kconfig

@@ -0,0 +1,24 @@
+# This file is used when packaging libcanard
+# for the ESP-IDF component registry:
+# https://components.espressif.com/
+
+# This file defines customizable ESP-IDF build options
+# that can be configured by running 'idf.py menuconfig'.
+
+menu "Libcanard"
+
+config CANARD_ASSERTIONS
+    bool "Enable libcanard assertions."
+    default y
+    help
+        Set to 'n' to disable libcanard assertions.
+
+config CANARD_CRC_TABLE
+    bool "Enable libcanard CRC table"
+    default y
+    help
+        Set to 'n' to use slow but ROM-efficient transfer-CRC computation algorithm.
+        Doing so is expected to save ca. 500 bytes of ROM and
+        increase the cost of RX/TX transfer processing by ~half.
+
+endmenu

esp_metadata/idf_component.yml

@@ -0,0 +1,12 @@
+# This file is used when packaging libcanard
+# for the ESP-IDF component registry:
+# https://components.espressif.com/
+
+# Note: Version is not specified in this file,
+# because the 'esp_publish.yml' GitHub action
+# automatically sets it based on the release version.
+
+description: "Cyphal/CAN for embedded systems."
+license: "MIT"
+url: "https://github.com/OpenCyphal/libcanard"
+repository: "https://github.com/OpenCyphal/libcanard"

esp_metadata/package_esp_component.sh

@@ -0,0 +1,26 @@
+#!/bin/bash
+set -e
+
+# This script must be called from the root of this repository.
+# It packages up libcanard as an ESP-IDF component in package/libcanard.
+
+mkdir -p package/libcanard/include
+
+cp CONTRIBUTING.md                  package/libcanard/CONTRIBUTING.md
+cp LICENSE                          package/libcanard/LICENSE
+cp README.md                        package/libcanard/README.md
+
+cp libcanard/canard.c               package/libcanard/canard.c
+cp libcanard/_canard_cavl.h         package/libcanard/_canard_cavl.h
+cp libcanard/canard.h               package/libcanard/include/canard.h
+
+cp esp_metadata/CMakeLists.txt      package/libcanard/CMakeLists.txt
+cp esp_metadata/Kconfig             package/libcanard/Kconfig
+cp esp_metadata/idf_component.yml   package/libcanard/idf_component.yml
+
+# Install compote, a tool for uploading ESP-IDF components.
+python3 -m pip install --upgrade idf-component-manager
+
+echo "Successfully packaged ESP component into package/libcanard:"
+find package/libcanard
+echo