Add yarn pack validation (#1315)

Summary:
Adds a step to validate the prepublish steps, and upload the resulting tarball.

Pull Request resolved: https://github.com/facebook/yoga/pull/1315

Test Plan: A tarball is uploaded as part of validation and looks decent.

Reviewed By: cortinico

Differential Revision: D47068368

Pulled By: NickGerleman

fbshipit-source-id: 62c8946a1bb542310634c8a7384a0e4890b35bdf

.github/workflows/validate-js.yml

@@ -72,3 +72,21 @@ jobs:
       - name: yarn lint
         run: yarn lint
         working-directory: javascript
+
+  pack:
+    name: Pack
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+
+      - name: Setup
+        uses: ./.github/actions/setup-js
+
+      - name: yarn pack
+        run: yarn pack --filename yoga-layout.tar.gz
+        working-directory: javascript
+
+      - uses: actions/upload-artifact@v3
+        with:
+          name: npm-package
+          path: javascript/yoga-layout.tar.gz