added a build-typings script

scripts/build-typings.js

@@ -0,0 +1,9 @@
+#!/usr/bin/env node
+const sh = require('shelljs')
+const vars = require('./vars')
+const log = require('npmlog')
+
+vars.builtinPlugins.forEach(plugin => {
+    log.info('typings', plugin)
+    sh.exec(`npx tsc --project ${plugin}/tsconfig.typings.json`)
+})