docs(VSCode): Recommend GitHub Actions extension

GitHub recently released the public beta of this extension. It provides
helpful context when editing GitHub Actions workflows and, when signed
in with your GitHub account, the status of relevant workflows.

Author: Kurt-von-Laven

.vscode/extensions.json

@@ -3,6 +3,7 @@
     "davidanson.vscode-markdownlint",
     "editorconfig.editorconfig",
     "esbenp.prettier-vscode",
+    "github.vscode-github-actions",
     "ms-azuretools.vscode-docker",
     "ms-python.python",
     "ms-vscode-remote.remote-containers",