doc(index): link to doc.rs for APIs

We also link more specifically to crates.io.

Some debt was taken on as the build_version is special and
duplicated right now.

etc/api/type-api.yaml

@@ -25,6 +25,7 @@ make:
     - source: build.rs
       output_dir: src
 cargo:
+  build_version: "1.0.0"
   build_script: src/build.rs
   keywords: [protocol, web, api]
   doc_base_url: https://docs.rs