Document how to integrate apps with libSQL with Wasm support

Due to the fact that our WebAssembly runtime is implemented in Rust, it's also not part of the customary sqlite3.c amalgamation file. Instead, users are expected to either:

• integrate directly with our Rust bindings crate, if libSQL is integrated into a Rust project, or
• statically link with a .libs/libwblibsql.a library, either compiled from source or precompiled, or
• link dynamically by using the dynamic flavor of the library, or building from source with ./configure --enable-wasm-runtime

These steps might be obvious enough for libSQL maintainers, but aren't for users, so they need to be clearly documented and easily available.

Refs #116