This commit removes the Lightbeam backend from Wasmtime as per [RFC 14].
This backend hasn't received maintenance in quite some time, and as [RFC
14] indicates this doesn't meet the threshold for keeping the code
in-tree, so this commit removes it.
A fast "baseline" compiler may still be added in the future. The
addition of such a backend should be in line with [RFC 14], though, with
the principles we now have for stable releases of Wasmtime. I'll close
out Lightbeam-related issues once this is merged.
[RFC 14]: https://github.com/bytecodealliance/rfcs/pull/14
* Start a high-level architecture document for Wasmtime
This commit cleands up some existing documentation by removing a number
of "noop README files" and starting a high-level overview of the
architecture of Wasmtime. I've placed this documentation under the
contributing section of the book since it seems most useful for possible
contributors.
I've surely left some things out in this pass, and am happy to add more!
* Review comments
* More rewording
* typos
