Add WIP changelog and update discrepancies in Docs

[pema99]

Please read:

• Changelog is a skeleton and needs to be filled out if we go with it.
• I fixed the major discrepancies in the docs, however:
  • A few of the functions in AudioLink.cginc are still not described (such as ALDecodeDataAsFloat)
  • The table 'Table for does it make sense to index with?' maybe should be updated, I'm not sure. I'll let Charles look.

[pema99]

https://keepachangelog.com/en/1.0.0/