Remove package-lock.json (#104)

* Remove package-lock.json

As per [the npm documentation](https://docs.npmjs.com/cli/v8/configuring-npm/package-lock-json#package-lockjson-vs-npm-shrinkwrapjson):

> ...`package-lock.json` cannot be published, and it will be
ignored if found in any place other than the root project.

* Update CI workflow to use npm install

`npm ci` only works if you have a `package-lock.json` or
`npm-shrinkwrap.json` file.

Author: simonplend

Diff for: .github/workflows/ci.yml

@@ -23,6 +23,6 @@ jobs:
       uses: actions/setup-node@v1
       with:
         node-version: ${{ matrix.node-version }}
-    - run: npm ci
+    - run: npm install
     - run: npm test
     - run: npm test -- --coverage-report=text-lcov | npx codecov --pipe

Diff for: .npmrc

@@ -0,0 +1 @@
+package-lock=false