ignore .github files in export

Author: sgiehl

.gitattributes

@@ -48,6 +48,7 @@ plugins/*/tests/UI/expected-screenshots/*.png filter=lfs diff=lfs merge=lfs
 
 # Files excluded from git packages
 tests/ export-ignore
+.github/ export-ignore
 .coveralls.yml export-ignore
 .gitignore export-ignore
 .gitattributes export-ignore