Updates grunt-contrib-jshint due to a bug with building.

See https://goo.gl/oUmN6c

Removes some unused variables and globals.
Refactors one unused variable to be used.

Generated eslintrc.json with `eslint --init` with the following config:

```
? How would you like to configure ESLint? Inspect your JavaScript file(s)
? Which file(s), path(s), or glob(s) should be examined? css.js
? What format do you want your config file to be in? JSON
? Are you using ECMAScript 6 features? No
? Where will your code run? Browser
? Do you use CommonJS? Yes
? Do you use JSX? No
```

Updates URLs in package & Grunt Bug + package-lock.json

Linting

Bumps [grunt](https://github.com/gruntjs/grunt) from 1.0.2 to 1.3.0.
- [Release notes](https://github.com/gruntjs/grunt/releases)
- [Changelog](https://github.com/gruntjs/grunt/blob/main/CHANGELOG)
- [Commits](gruntjs/grunt@v1.0.2...v1.3.0)

---
updated-dependencies:
- dependency-name: grunt
  dependency-type: direct:development
...

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