Add ColorSchemeUnit support

[gerardroche]

Allows running the ColorSchemeUnit tests.

Example

name: Continuous Integration

on: [push, pull_request]

env:
  PACKAGE: MonokaiFree

jobs:
  tests:
    strategy:
      fail-fast: false
      matrix:
        st-version: [3, 4]
        os: ["ubuntu-latest", "macOS-latest", "windows-latest"]
    runs-on: ${{ matrix.os }}
    steps:
      - name: Checkout
        uses: actions/checkout@v3

      - name: Setup
        uses: SublimeText/UnitTesting/actions/setup@v1
        with:
          sublime-text-version: ${{ matrix.st-version }}
          package-name: ${{ env.PACKAGE }}

      - name: Color Scheme Tests
        uses: SublimeText/UnitTesting/actions/run-color-scheme-tests@v1