feat: implement a migrator that updates the project's ts version

Author: haoqunjiang

packages/@vue/cli-plugin-typescript/migrator/index.js

@@ -0,0 +1,7 @@
+module.exports = (api) => {
+  api.extendPackage({
+    devDependencies: {
+      typescript: require('../package.json').devDependencies.typescript
+    }
+  }, true)
+}