Add Scaffold command for npm users (umijs#5035)

release: v3.3.0-alpha.0

release: v3.2.9

release: v3.2.8

release: v3.2.7

release: v3.2.6

release: v3.2.5

release: v3.2.4

release: v3.2.3

release: v3.2.2