Add Sass support

[judehunter]

Fixes #67

Adds support for indented sass syntax.
It's done with an indentedSyntax conditional field/option which depends on the file type (.sass for indented syntax, .scss for the one with braces) when rendering to css with the sass module.

I decided to omit some fixtures and such because it wouldn't matter whether the original file imported a .sass or .scss file.

Working autocompletion with indented sass:

[judehunter]

For some reason the CI test task fails (on snapshots, it seems), though running npm test on my machine with the updated snapshots worked flawlessly. I might have screwed something up. 😕

[mrmckeb]

Hi @judehunter, I think you ran into this issue because you were using npm. You may have had a different module resolve somewhere, and that's why your snapshots are different.

I ran locally on a clean checkout of your repo - yarn && yarn test -u - and updated snapshots, and then pushed. It is all good now ;)

[mrmckeb]

Thanks @judehunter, this is now out in v2.1.2.
https://github.com/mrmckeb/typescript-plugin-css-modules/releases/tag/v2.1.2

Great work!