[1.x] Update .gitattributes to exclude playgrounds/ from linguist inf…

…erence (#1903)

* Update .gitattributes to exclude playgrounds/ from linguist inference

* Update .gitattributes

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Co-authored-by: Joe Tannenbaum <joe.tannenbaum@laravel.com>

.gitattributes

@@ -1 +1,5 @@
+# exclude playgrounds/ since otherwise the project gets classified as mainly php based.
+# https://github.com/github-linguist/linguist/blob/master/docs/overrides.md#summary
+playgrounds/** linguist-vendored
+
 * text=auto