Regularly test against next builds of React

Test against react@next Once a week on Monday

Close #1484
Close #2318

.github/workflows/react-integration.yml

@@ -0,0 +1,21 @@
+name: react@next integration
+
+on:
+  schedule:
+    # Run every Monday at 12:00 (see https://crontab.guru)
+    - cron: '0 12 * * 1'
+
+jobs:
+  react-next:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+    - uses: actions/setup-node@v1
+      with:
+        node-version: '14.x'
+    - run: npm install -g yarn
+    - run: yarn install
+    # Install next-tagged versions
+    - run: yarn upgrade react@next react-dom@next -W --dev
+    # Only run the unit tests
+    - run: yarn jest

package.json

@@ -27,7 +27,7 @@
     "prerelease": "yarn test && yarn compile",
     "release": "node ./scripts/release/publish.js",
     "postrelease": "yarn docs:release && yarn benchmarks:release",
-    "test": "yarn flow && yarn lint:report && yarn jest --runInBand"
+    "test": "yarn flow && yarn fmt:report && yarn lint:report && yarn jest --runInBand"
   },
   "devDependencies": {
     "@babel/cli": "^7.12.13",