Use memfs to bring up more nodejs toolings

[3cp]

memfs can run in browser.

Few things we can do with memfs:

1. bring Stylus up in browser.
2. replace sass.js (ecmascripted libsass) with sass (dart-sass).

• but surprisingly, sass is not much smaller than sass.js (3.5MB vs 4.4MB).

3. bring vue component compiler up in browser.