Exclude vendor dirs from git CRLF normalization (#10911)

* Exclude vendor dirs from git CRLF normalization

Should get rid of a few warnings like at the end of `lint-backend` like
https://drone.gitea.io/go-gitea/gitea/23117/1/4

* make vendor

Co-authored-by: John Olheiser <john.olheiser@gmail.com>
Co-authored-by: guillep2k <18600385+guillep2k@users.noreply.github.com>

.gitattributes

@@ -1,4 +1,7 @@
 * text=auto eol=lf
+/vendor/** -text -eol
+/public/vendor/** -text -eol
+
 conf/* linguist-vendored
 docker/* linguist-vendored
 options/* linguist-vendored