Quasar Plugin installs node-sass, even if dart-sass is already installed

[eagerestwolf]

Describe the bug
When setting up a Vue application using the Vue CLI, users are given the option to install either node-sass or dart-sass. When installing Quasar with the Vue CLI and selecting Sass or SCSS as the CSS processor, Quasar installs node-sass, even if dart-sass is installed.

To Reproduce
Steps to reproduce the behavior:

1. Create a Vue application using the Vue CLI (vue create [appname])
2. Manually select features
3. Select CSS Pre-processors option
4. Select Sass/SCSS (with dart-sass)
5. Finish setting up app with Vue CLI
6. Change to app folder (cd [appname])
7. Install Quasar (vue add quasar)
8. During Quasar setup, select either Sass with indented syntax or Sass with SCSS syntax

Expected behavior
Quasar should not install a Sass pre-processor at all. It's the responsibility of Vue to compile the Sass, not Quasar. However, if you want to ensure the user has a Sass pre-processor installed, you should check for either node-sass or dart-sass.

Platform:
OS: Windows 10 (Build 18363.535)
Node: 12.13.1
NPM: 6.13.1
Yarn: 1.21.1
Browsers: Microsoft Edge (Version 44.18362.449.0), Google Chrome (Version 79.0.3945.88)

Additional context
It should also be noted that if you are going to default to node-sass or dart-sass, you should default to dart-sass anyway because that's the preferred implementation by the Sass development team (reference), and it's significantly faster than node-sass anyway.