Start adopting Yarn workspaces (#985)

* Start adopting Yarn workspaces

My plan is to move the existing package into a workspace and then split
out the things that really ought to be their own packages. For example,
the demo site and the experiments really ought to be separate.

Fix lint command

* Use workspaces in CI

* Fix deploy for monorepo

.github/workflows/nodejs.yml

@@ -20,16 +20,16 @@ jobs:
         run: yarn
       - name: Lint
         run: |
-          yarn lint
-          yarn type-check
+          yarn workspace webamp lint
+          yarn workspace webamp type-check
       - name: Build
         run: |
-          yarn build
-          yarn build-library
+          yarn workspace webamp build
+          yarn workspace webamp build-library
       - name: Run Unit Tests
-        run: yarn test
+        run: yarn workspace webamp test
       - name: Run Integration Tests
-        run: yarn integration-tests
+        run: yarn workspace webamp integration-tests
         env:
           CI: true
       - name: Upload Screenshot Diffs
@@ -37,14 +37,14 @@ jobs:
         uses: actions/upload-artifact@v1
         with:
           name: image_diffs
-          path: js/__tests__/__image_snapshots__/__diff_output__/
+          path: packages/webamp/js/__tests__/__image_snapshots__/__diff_output__/
       - name: Generate New Screenshots
         if: failure()
         run: |
-          yarn integration-tests -u
+          yarn workspace webamp integration-tests -u
       - name: Upload New Screenshots
         if: failure()
         uses: actions/upload-artifact@v1
         with:
           name: new_images
-          path: js/__tests__/__image_snapshots__/
+          path: packages/webamp/js/__tests__/__image_snapshots__/