Exclude more non-code from release tarballs

Author: glensc

.gitattributes

@@ -1,11 +1,15 @@
 # Path-based git attributes
 # https://www.kernel.org/pub/software/scm/git/docs/gitattributes.html
 
-# Ignore all test and documentation with "export-ignore".
+# Ignore dot files, test and documentation with "export-ignore".
+/.editorconfig      export-ignore
 /.gitattributes     export-ignore
+/.github            export-ignore
 /.gitignore         export-ignore
-/.travis.yml        export-ignore
-/phpunit.xml.dist   export-ignore
 /.scrutinizer.yml   export-ignore
+/.styleci.yml       export-ignore
+/CODE_OF_CONDUCT.md export-ignore
+/CONTRIBUTING.md    export-ignore
+/phpunit.xml.dist   export-ignore
 /test               export-ignore
-/docs               export-ignore
+/docs               export-ignore