Update README with popup screenshot and some store links.

Author: nedtwigg

.github/screenshot-popup.png

@@ -5,9 +5,18 @@
 - "Syntax highlighting is the lie that enables us to see the truth."
 - "The meaning of life is to find your lost comment drafts. The purpose of life is to post them."
 
-![screenshot of syntax highlighting in the edit pane of a GitHub issue](.github/screenshot_highlighting.png)
+## Install
 
-TODO: screenshot of comment draft index
+- Chrome Web Store TODO
+- [Microsoft Edge Add-on](https://microsoftedge.microsoft.com/addons/detail/gitcasso/agldcmiblfnebkjielmgcipekjhejihp)
+
+## Screenshots
+
+![screenshot of syntax highlighting in the edit pane of a GitHub issue](.github/screenshot-syntax.png)
+
+![screenshot of the draft history popup](.github/screenshot-popup.png)
+
+## Contributing
 
 If there's something you'd like to add or fix, see [CONTRIBUTING.md](CONTRIBUTING.md).