Update concrete5 gitignore (#3176)

Concrete5.gitignore

@@ -1,4 +1,21 @@
+# ignore the error log and .htaccess and others
+error_log
+.htaccess
+
+# concrete5 5.6 specific
+
 config/site.php
 files/cache/*
 files/tmp/*
-.htaccess
+
+# concrete5 5.7 specific
+
+# ignore everything but the index.html
+/application/files/*
+!/application/files/index.html
+
+# ignore updates folder
+/updates/*
+
+# ignore sitemap.xml
+/sitemap.xml