Provide pre-compiled shared libraries for C-API

[tschneidereit]

We should provide pre-compiled .so/.dylib/.dll files for the Wasmtime C-API implementation so people can use it without having a Rust development environment set up.

This should come with an example for how to use it, and probably a header file making it easy to use.

@yurydelendik, can you take this on?

[yurydelendik]

closed by #311