support react 16.14 (#166)

Updates answers-headless-react to the alpha version that
announces react 16.14 support.

Update unit tests to run in react 16 in addition to 17.

I tried to upgrade the lib to use react 18 as as a dev dep,
but we still have a few dependencies that don't allow for 18
like storybook/react.
I opened up an issue for that particular one, since I believe it's the only one.
storybookjs/storybook#18349 (comment)

J=SLAP-2113
TEST=manual,auto

run test-site with react 16, check dev tools to see it is using react-dom 16.14
update unit tests to run in react 16

.github/workflows/run-tests.yml

@@ -6,7 +6,15 @@ name: Run Tests
 on: [push, pull_request]
 
 jobs:
-  call_run_tests:
+  call_run_tests-react-17:
     uses: yext/slapshot-reusable-workflows/.github/workflows/run_tests.yml@v1
     with:
-      node_matrix: '["14.x", "16.x"]'
+      node_matrix: '["14.x", "16.x", "18.x"]'
+
+  call_run_tests-react-16:
+    uses: yext/slapshot-reusable-workflows/.github/workflows/run_tests.yml@v1
+    with:
+      build_script: |
+        npm i -D react@16.14 react-dom@16.14
+        npm run build
+      node_matrix: '["14.x", "16.x", "18.x"]'

package.json

@@ -73,8 +73,8 @@
     "typescript": "~4.4.3"
   },
   "peerDependencies": {
-    "@yext/answers-headless-react": "1.1.1-alpha.123",
-    "react": "^17 || ^18"
+    "@yext/answers-headless-react": "1.1.1-alpha.125",
+    "react": "^16.14 || ^17 || ^18"
   },
   "jest": {
     "bail": 0,