test: add a workflow which submits a mock test result

.github/workflows/example.yml

@@ -0,0 +1,17 @@
+on: push
+name: Example
+jobs:
+  example:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@master
+      - run: |
+          mkdir -p ./reports/junit/
+          cp ./example/junit.xml ./reports/junit/
+        # I can't find a way to make the branch name below dynamic, so we'l
+        # need to remember to adjust it when working on features.
+      - uses: check-run-reporter/action@master
+        env:
+          CHECK_RUN_REPORTER_LABEL: 'Unit Tests'
+          CHECK_RUN_REPORTER_REPORT: 'reports/junit/**/*.xml'
+          CHECK_RUN_REPORTER_TOKEN: ${{ secrets.CHECK_RUN_REPORTER_TOKEN }}

example/index.spec.js

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+describe('example', () => {
+  it('does not fail', () => {
+    expect(false).toBe(true);
+  });
+});

example/junit.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<testsuites name="Unit Tests" tests="1" failures="1" time="1.3">
+  <testsuite name="example" errors="0" failures="1" skipped="0" timestamp="2020-02-17T01:23:12" time="0.641" tests="1">
+    <testcase classname="example" name="does not fail" time="0.003">
+      <failure>Error: expect(received).toBe(expected) // Object.is equality
+
+Expected: true
+Received: false
+    at Object.&lt;anonymous&gt; (/github/workspace/example/index.spec.js:3:19)
+    at Object.asyncJestTest (/github/workspace/node_modules/jest-jasmine2/build/jasmineAsyncInstall.js:102:37)
+    at /github/workspace/node_modules/jest-jasmine2/build/queueRunner.js:43:12
+    at new Promise (&lt;anonymous&gt;)
+    at mapper (/github/workspace/node_modules/jest-jasmine2/build/queueRunner.js:26:19)
+    at /github/workspace/node_modules/jest-jasmine2/build/queueRunner.js:73:41</failure>
+    </testcase>
+  </testsuite>
+</testsuites>