ci: re-enable coveralls coverage upload

Reverts commits:
  - Disabling coveralls temporarilly
    aedf066337
  - Tmo disabling of coveralls
    a6b4cb24b8

I'm not 100% sure whether the `parallel` option is needed,
but I've left it disabled for now, since it'd would mean that we need
to merge both the `test.yml` and the `e2e.yml` file together.

.github/workflows/e2e

@@ -36,3 +36,9 @@ jobs:
       run: yarn e2e
       env:
         CYPRESS_CACHE_FOLDER: .cache/Cypress
+
+    - name: Upload Coverage to Coveralls
+        uses: coverallsapp/github-action@master
+        with:
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+          flag-name: e2e

.github/workflows/test.yml

@@ -32,3 +32,12 @@ jobs:
       - name: Run Unit Tests
         run: |
           yarn ci --coverage
+
+      - name: Upload Coverage to Coveralls
+        # it feels a bit weird to use @master, but that's what the docs use
+        # (coveralls also doesn't publish a @v1 we can use)
+        # https://github.com/marketplace/actions/coveralls-github-action
+        uses: coverallsapp/github-action@master
+        with:
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+          flag-name: unit