fix: use regex patterns in lycheeignore

Author: Drew Stone

.lycheeignore

@@ -3,5 +3,5 @@ https://localhost*
 # Testnet explorer returns 401 but links are valid
 https://testnet-explorer.tangle.tools/*
 # Internal MDX routes without .mdx extension (valid Nextra routes, not filesystem paths)
-**/claim-airdrop
-**/join_operator/join
+.*/claim-airdrop$
+.*/join_operator/join$