Improve Gitpod automated setup (#3880)

* Gitpod is no longer in Beta

* Automatically open the web preview on start-up in Gitpod

* Accelerate Gitpod start-up with continuously prebuilt workspaces

* Install Prettier VS Code extension in Gitpod

.gitpod.yml

@@ -1,5 +1,27 @@
 ports:
   - port: 8080
+    onOpen: open-preview
 tasks:
   - init: npm ci && npm run build
     command: node server 8080 0.0.0.0
+github:
+  prebuilds:
+    # enable for the master/default branch (defaults to true)
+    master: true
+    # enable for all branches in this repo (defaults to false)
+    branches: true
+    # enable for pull requests coming from this repo (defaults to true)
+    pullRequests: true
+    # enable for pull requests coming from forks (defaults to false)
+    pullRequestsFromForks: true
+    # add a check to pull requests (defaults to true)
+    addCheck: true
+    # add a "Review in Gitpod" button as a comment to pull requests (defaults to false)
+    addComment: true
+    # add a "Review in Gitpod" button to the pull request's description (defaults to false)
+    addBadge: false
+    # add a label once the prebuild is ready to pull requests (defaults to false)
+    addLabel: false
+vscode:
+  extensions:
+    - esbenp.prettier-vscode@1.7.0:EbyqFvwe32qQBptkOgfQpQ==