* Spice up the project README, fill out more docs
This is an attempt to spruce up wasmtime's README.md file as well as
fill out more of the missing documentation in the `docs/` folder.
There's still a long way to go but I hoped here to mostly move around
existing information and add new information. As always happy to have
feedback!
* Tweak CLI wording
* Remove no-longer relevant clause
* Update sandboxing docs
* Handle comments
I thought it might be useful for future WASI users to have the WASI tutorial written not only in C but also in Rust.
I'm also happy to keep the tutorial up to date with the current state of WASI target in Rust.
Document that `setjmp`/`longjmp` and C++ exceptions are unsupported, and
update the documentation about the function signature mismatch bug to
reflect that it's now just a warning rather than a fatal error.
