Miscellaneous doc updates (#1383)

* Add additional links to embedding and tutorial documentation.

* Fix a broken link to CONTRIBUTING.md.

Fixes #1280.

crates/jit/README.md

@@ -2,5 +2,9 @@ This is the `wasmtime-jit` crate, which contains JIT-based execution
 for wasm, using the wasm ABI defined by [`wasmtime-environ`] and the
 runtime support provided by [`wasmtime-runtime`].
 
+Most users will want to use the main [`wasmtime`] crate instead of using this
+crate directly.
+
 [`wasmtime-environ`]: https://crates.io/crates/wasmtime-environ
 [`wasmtime-runtime`]: https://crates.io/crates/wasmtime-runtime
+[`wasmtime`]: https://crates.io/crates/wasmtime

crates/runtime/README.md

@@ -5,6 +5,10 @@ support, supporting the wasm ABI used by [`wasmtime-environ`],
 This crate does not make a host vs. target distinction; it is meant to be
 compiled for the target.
 
+Most users will want to use the main [`wasmtime`] crate instead of using this
+crate directly.
+
 [`wasmtime-environ`]: https://crates.io/crates/wasmtime-environ
 [`wasmtime-jit`]: https://crates.io/crates/wasmtime-jit
 [`wasmtime-obj`]: https://crates.io/crates/wasmtime-obj
+[`wasmtime`]: https://crates.io/crates/wasmtime