Add link to Changelog in the docs

docs/index.md

@@ -1,5 +1,7 @@
 # Heynote Documentation
 
+[Changelog](https://heynote.com/docs/changelog/)
+
 Heynote is a dedicated scratchpad for developers. It functions as a large persistent text buffer where you can write down anything you like. Works great for that Slack message you don't want to accidentally send, a JSON response from an API you're working with, notes from a meeting, your daily to-do list, etc. 
 
 The Heynote buffer is divided into blocks, and each block can have its own Language set (e.g. JavaScript, JSON, Markdown, etc.). This gives you syntax highlighting and lets you auto-format that JSON response.