readme: add link to wiki page on developing outside of docker-compose

Author: pietroalbini

README.md

@@ -91,7 +91,11 @@ cargo test
 Some tests require access to the database. To run them, set the
 `CRATESFYI_DATABASE_URL` to the url of a PostgreSQL database. You don't have to
 run the migrations on it or ensure it's empty, as all the tests use temporary
-tables to prevent conflicts with each other or existing data.
+tables to prevent conflicts with each other or existing data. See the [wiki
+page on developing outside docker-compose][wiki-no-compose] for more
+information on how to setup this environment.
+
+[wiki-no-compose]: https://github.com/rust-lang/docs.rs/wiki/Developing-without-docker-compose
 
 ### Docker-Compose