docs: include crate links

Author: calebcartwright

README.md

@@ -2,6 +2,6 @@
 
 Repository for automatically publishing the below crates once a week.
 
-- `rustc-ap-rustc_ast`
-- `rustc-ap-rustc_expand`
-- `rustc-ap-rustc_parse`
+- [rustc-ap-rustc_ast](https://crates.io/crates/rustc-ap_rustc_ast)
+- [rustc-ap-rustc_expand](https://crates.io/crates/rustc-ap_rustc_expand)
+- [rustc-ap-rustc_parse](https://crates.io/crates/rustc-ap_rustc_parse)