Removing README from export ignore (can be useful)

Author: moufmouf

.gitattributes

@@ -2,7 +2,6 @@
 /.gitignore export-ignore
 /.travis.yml export-ignore
 /CONTRIBUTING.md export-ignore
-/README.md export-ignore
 /phpcs.xml.dist export-ignore
 /phpstan.neon export-ignore
 /benchmark export-ignore