LAKE SUCCESS, March 29.-(AP)-The United Nations Palestine commission decided tonight to proceed as rapidly as possible to create a provisional Jewish government in Palestine. The decision was announced in a letter to Moshe Shertok, head of the political department of the Jewish Agency. A high U. N. official said the agreement was unanimous. The decision came a few hours after a spokesman for the United States delegation disclosed that Chief Delegate Warren R. Austin would go before the Security Council tomorrow to appeal for a truce in Palestine.