Suggestion: Glossary

[cecille]

Why is this content needed
It's just nice to have a central location to look up some of the acryonyms and terms we use on a regular basis.

Who will benifit,
This would mostly be aimed at developers who are new to Matter.

Are you able and willing to create the content
yes, well, a start at least. #27

Additional context
I don't know how to build the site so I have no idea if those headers are correct or whether it makes sense to have the whole thing in an index. If you add corrections on the PR, I can make the fixes.