Increase visibility of language aliases note

Add a Important alert to the note about using language aliases

Author: tspascoal

README.md

@@ -22,6 +22,7 @@ Using a `githubsecuritylab/codeql-LANG-queries` query pack will reference the de
 
 ### Using a community pack from the CodeQL Action
 
+> [!IMPORTANT]
 > For language aliases in `strategy.matrix.language`, use `cpp` instead of `c-cpp`, `java` instead of `java-kotlin` and `javascript` instead of `javascript-typescript`.
 
 ```yaml