[Build] Support for scss modules

[RaananW]

css modules is a way to import a css and get a list of classes from it that can be applied to the specific moduels used in a component. It is tree-shaking friendly and a very good practice to avoid global css changes cross-projects.

This step provides support in our build system for both modules and global scss. If the .scss file is called whatever.modules.scss it will be loaded as a module. See the shared ui components project for an example.

[azure-pipelines]

Please make sure to label your PR with "bug", "new feature" or "breaking change" label(s).
To prevent this PR from going to the changelog marked it with the "skip changelog" label.

[azure-pipelines]

Snapshot stored with reference name:
refs/pull/12832/merge

Test environment:
https://babylonsnapshots.z22.web.core.windows.net/refs/pull/12832/merge/index.html

To test a playground add it to the URL, for example:

https://babylonsnapshots.z22.web.core.windows.net/refs/pull/12832/merge/index.html#WGZLGJ#4600

Links to test babylon tools with this snapshot:

https://playground.babylonjs.com/?snapshot=refs/pull/12832/merge
https://sandbox.babylonjs.com/?snapshot=refs/pull/12832/merge
https://gui.babylonjs.com/?snapshot=refs/pull/12832/merge
https://nme.babylonjs.com/?snapshot=refs/pull/12832/merge

To test the snapshot in the playground with a playground ID add it after the snapshot query string:

https://playground.babylonjs.com/?snapshot=refs/pull/12832/merge#BCU1XR#0