Add documentation for In Memory File System

[stupendoussuperpowers]

This adds a brief design documentation for the in memory file system.

[Yaxuan-w]

Awesome!

[stupendoussuperpowers]

Have made the suggested changes and polished up the structure a bit. I've also added more comments on the IMFS source code.

[rennergade]

This looks great.

My only questions here are more to the group as a whole, since this is about a grate (and I'm guessing we'll also merge the grate code somewhere) where should the docs for this as well as the grate code live logically in the repository?

[stupendoussuperpowers]

Might make sense to have a top-level folder for all example grates, since they are compiled out-of-tree. (e.g./lind-wasm/example_grates/imfs)

Not sure which would be better for the docs: each example grate having a readme.md doc file along side the code, or having all of them within an example_grates folder within docs

[rennergade]

Yeah agree there. My inclination is to include them in a readme alongside the code since they're not really a part of the main codebase?

[rennergade]

I think this has been ported to a new repo so lets close this PR.

[stupendoussuperpowers]

Moved to: Lind-Project/lind-wasm-example-grates#4