Update Docs/Guide__Installing.md

Co-authored-by: Davide Violante <DavideViolante@users.noreply.github.com>

Docs/Guide__Installing.md

@@ -191,7 +191,8 @@ For now, you can try this
 
 ##### App from Play Store
 
-- Although app(s) which use this API exist but they aren't official.
+- Although app(s) which use this API exist, they aren't official.
+
   
 ##### On Firefox