Add link to github PR that fixed an issue

Author: NlightNFotis

MINI-PROJECTS.md

@@ -114,4 +114,4 @@ Completed
 `--show-goto-functions`, by printing out the `irep` of every program
 instruction instead of a concise representation.
 
-*Completed in* PR #991
+*Completed in* [PR #991](https://github.com/diffblue/cbmc/pull/991)