how to update app framework from 1.20 to 3.0

[Feng]

It cause a problem when I do this: npm install app-framework@latest,

I cancel eslint test.

then, the const relAppPath in update-main-file.js was wrong,like this:

before: const relAppPath = path.relative(path.cache(), path.app())

I modify: const relAppPath = path.relative(path.cache(), path.app()).replace(/\\/g,'\/')

while open browser at localhost:1234, there is nothing.

and chrome console print "[vue warn]", login-popup can't be found in app.vue