Document the Release Candidate process (#13718)

# Objective

- Document how to release a RC

## Solution

- Also allow CI to trigger on release branches

.github/workflows/ci.yml

@@ -6,6 +6,7 @@ on:
   push:
     branches:
       - main
+      - release-*
 
 env:
   CARGO_TERM_COLOR: always

.github/workflows/validation-jobs.yml

@@ -6,6 +6,7 @@ on:
   push:
     branches:
       - main
+      - release-*
 
 concurrency:
   group: ${{github.workflow}}-${{github.ref}}

docs/release_checklist.md

@@ -64,3 +64,24 @@
     1. Discord: Bevy
 
 ### Patch Post-Release
+
+## Release Candidate
+
+### RC Pre-Release
+
+1. Check appropriate milestone.
+2. Create a branch for the release.
+3. Bump version number for all crates, using the command from the "Release" workflow locally, with `rc` for the new version. At the time of writing this:
+    * `cargo release rc --workspace --no-publish --execute --no-tag --no-confirm --no-push --dependent-version upgrade --exclude ci --exclude errors --exclude bevy_mobile_example --exclude build-wasm-example`
+    * Change the commit message to be nicer
+4. Create tag on GitHub.
+5. Edit Github Release. Add link to the comparison between this rc and the previous version.
+
+### RC Release
+
+1. Release on crates.io
+    * `bash tools/publish.sh`
+2. Announce on:
+    1. Discord: Bevy, #dev-announcements
+
+### RC Post-Release