feat: support filtering users table by login type (#17238)

#15896 Mentions ability to add support for filtering by login type

The issue mentions that backend API support exists but the backend did
not seem to have the support for this filter. So I have added the
ability to filter it.

I also added a corresponding update to readme file to make sure the docs
will correctly showcase this feature

coderd/database/queries/users.sql

@@ -260,6 +260,12 @@ WHERE
 			github_com_user_id = @github_com_user_id
 		ELSE true
 	END
+	-- Filter by login_type
+	AND CASE
+		WHEN cardinality(@login_type :: login_type[]) > 0 THEN
+			login_type = ANY(@login_type :: login_type[])
+		ELSE true
+	END
 	-- End of filters
 
 	-- Authorize Filter clause will be injected below in GetAuthorizedUsers