Add more links to main docs page

docs/README.md

@@ -13,13 +13,21 @@ Index
 - [Testing the API with cURL](Using-the-API/Testing-with-cURL.md)
 - [OAuth details](Using-the-API/OAuth-details.md)
 - [Tips for app developers](Using-the-API/Tips-for-app-developers.md)
+- [Push notifications](Using-the-API/Push-notifications.md)
 
 ### Running Mastodon
 - [Production guide](Running-Mastodon/Production-guide.md)
+- [Alternative: Running on Heroku](Running-Mastodon/Heroku-guide.md)
 - [Development guide](Running-Mastodon/Development-guide.md)
+- [Alternative: Development with Vagrant](Running-Mastodon/Vagrant-guide.md)
 - [Administration guide](Running-Mastodon/Administration-guide.md)
 
 ### Contributing to Mastodon
 - [Sponsors](Contributing-to-Mastodon/Sponsors.md)
 - [Translate Mastodon in your language](Contributing-to-Mastodon/Translating.md)
 - [Report bugs and submit ideas](https://github.com/tootsuite/mastodon/issues)
+
+### Protocols
+
+- [List of used specs and RFCs for the federation](Specs-and-RFCs-used.md)
+- [Extensions of the above protocols](Extensions.md)