Setup Gitpod (#11704)

Co-authored-by: Brian Ng <bng412@gmail.com>

[skip ci]

.gitpod.yml

@@ -0,0 +1,22 @@
+# List the start up tasks. You can start them in parallel in multiple terminals. See https://www.gitpod.io/docs/config-start-tasks/
+tasks:
+  - init: make bootstrap
+    command: make watch
+
+github:
+  # https://www.gitpod.io/docs/prebuilds/#configure-prebuilds
+  prebuilds:
+    master: true
+    branches: true
+    pullRequests: true
+    pullRequestsFromForks: true
+    addCheck: true
+    addComment: false
+    addBadge: true
+    addLabel: false
+
+vscode:
+  extensions:
+    - dbaeumer.vscode-eslint@2.1.5:9Wg0Glx/TwD8ElFBg+FKcQ==
+    - esbenp.prettier-vscode@5.0.0:qca7d0cHbKkrkb5rvNlpcg==
+    - flowtype.flow-for-vscode@1.5.0:AwOT6wgHTF43loZQCAUMLA==

CONTRIBUTING.md

@@ -18,6 +18,8 @@
 
 Contributions are always welcome, no matter how large or small! Before contributing, please read the [code of conduct](https://github.com/babel/babel/blob/master/CODE_OF_CONDUCT.md).
 
+If you want an already configured online IDE to contribute to Babel, you can use [Gitpod](https://gitpod.io/#https://github.com/babel/babel)!
+
 ## Not sure where to start?
 
 - If you aren't just making a documentation change, you'll probably want to learn a bit about a few topics.

README.md

@@ -8,6 +8,9 @@
   The compiler for writing next generation JavaScript.
 </p>
 
+<p align="center">
+[![Gitpod ready-to-code](https://img.shields.io/badge/Gitpod-ready--to--code-blue?logo=gitpod)](https://gitpod.io/#https://github.com/babel/babel)
+</p>
 <p align="center">
     <a href="https://www.npmjs.com/package/@babel/core"><img alt="v7 npm Downloads" src="https://img.shields.io/npm/dm/@babel/core.svg?maxAge=43200&label=v7%20downloads"></a>
   <a href="https://www.npmjs.com/package/babel-core"><img alt="v6 npm Downloads" src="https://img.shields.io/npm/dm/babel-core.svg?maxAge=43200&label=v6%20downloads"></a>