Add suport for gitlab.cn

Author: sunny0826

README.md

@@ -1,7 +1,7 @@
 # Gitpod Browser extension
 [![Setup Automated](https://img.shields.io/badge/setup-automated-blue?logo=gitpod)](https://gitpod.io/#https://github.com/gitpod-io/browser-extension)
 
-This is the browser extension for Gitpod. It supports Chrome (see [Chrome Web Store](https://chrome.google.com/webstore/detail/dodmmooeoklaejobgleioelladacbeki/)), Firefox (see [Firefox Add-ons](https://addons.mozilla.org/firefox/addon/gitpod/)) and Edge (see [how to install Chrome extensions](https://support.microsoft.com/help/4538971/microsoft-edge-add-or-remove-extensions)), and adds a **Gitpod** button to the configured GitLab, GitHub and Bitbucket installations (defaults to `gitlab.com`, `github.com` and `bitbucket.org`) which immediately creates a Gitpod workspace for the current Git context:
+This is the browser extension for Gitpod. It supports Chrome (see [Chrome Web Store](https://chrome.google.com/webstore/detail/dodmmooeoklaejobgleioelladacbeki/)), Firefox (see [Firefox Add-ons](https://addons.mozilla.org/firefox/addon/gitpod/)) and Edge (see [how to install Chrome extensions](https://support.microsoft.com/help/4538971/microsoft-edge-add-or-remove-extensions)), and adds a **Gitpod** button to the configured GitLab, GitHub and Bitbucket installations (defaults to `gitlab.com`, `github.com` , `bitbucket.org` and `gitlab.cn`) which immediately creates a Gitpod workspace for the current Git context:
 
  ![Gitpodify](./docs/github-injected.png "Gitpodify")
 

manifest.json

@@ -15,6 +15,7 @@
         "*://*.github.com/*",
         "*://*.gitlab.com/*",
         "*://*.bitbucket.org/*",
+        "*://*.gitlab.cn/*",
         "*://*.gitpod.io/*"
       ],
       "js": [