Measure test coverage (#16)

* define npm run coverage

* Revert "define npm run coverage"

This reverts commit 32133d33412105d167226ac31c4f7875f85716ab.

* use coverallsapp/github-action@master

* Give --coverage option to npm test

* Add coveralls badge

.github/workflows/test.yml

@@ -14,10 +14,13 @@ jobs:
     - run: |
         npm install
         npm run all
+    - uses: coverallsapp/github-action@master
+      with:
+        github-token: ${{ secrets.GITHUB_TOKEN }}
   test: # make sure the action works on a clean machine without building
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v1
     - uses: ./
-      with: 
-        milliseconds: 1000
+      with:
+        issue_title: npm audit run by test job