feat: add gitpod configuration

Signed-off-by: nscuro <nscuro@protonmail.com>

.gitpod.Dockerfile

@@ -0,0 +1,10 @@
+FROM gitpod/workspace-go:2022-02-04-10-54-10@sha256:8ea7684f6b1294c21065918880e6f31d16ac58b61361754b8d384b8e8f8279ae
+
+USER root
+
+RUN \
+    wget -O "/usr/local/bin/cyclonedx" https://github.com/CycloneDX/cyclonedx-cli/releases/download/v0.22.0/cyclonedx-linux-x64 && \
+    echo "ae39404a9dc8b2e7be0a9559781ee9fe3492201d2629de139d702fd4535ffdd6 /usr/local/bin/cyclonedx" | sha256sum -c && \
+    chmod +x "/usr/local/bin/cyclonedx"
+
+USER gitpod

.gitpod.yml

@@ -0,0 +1,9 @@
+image:
+  file: .gitpod.Dockerfile
+
+tasks:
+  - init: make build
+
+vscode:
+  extensions:
+    - golang.Go

README.md

@@ -47,6 +47,8 @@ See the [LICENSE](./LICENSE) file for the full license.
 
 ## Contributing
 
+[![Open in Gitpod](https://gitpod.io/button/open-in-gitpod.svg)](https://gitpod.io/#https://github.com/CycloneDX/cyclonedx-go)
+
 Pull requests are welcome. But please read the
 [CycloneDX contributing guidelines](https://github.com/CycloneDX/.github/blob/master/CONTRIBUTING.md) first.
 
@@ -57,5 +59,4 @@ supported Go versions (see [Compatibility](#compatibility)) for every pull reque
 
 Some tests make use of the [CycloneDX CLI](https://github.com/CycloneDX/cyclonedx-cli), e.g. to validate BOMs.  
 Make sure to download the CLI binary and make it available as `cyclonedx` in your `$PATH`.  
-See also *Setup CycloneDX CLI* in
-the [workflow](https://github.com/CycloneDX/cyclonedx-go/blob/master/.github/workflows/ci.yml#L37).
+This is done automatically for [Gitpod](https://gitpod.io/#https://github.com/CycloneDX/cyclonedx-go).