Fix mocha option from colors -> color

[ppg]

This PR contains:

• [x] bugfix
• [ ] feature
• [ ] refactor
• [ ] tests
• [ ] documentation
• [ ] metadata

Breaking Changes?

• [x] yes
• [ ] no

Mocha v7 deprecates useColors in favor of color, and Mocha v8 and onwards don't support useColors. That means this fix of https://github.com/shellscape/mocha-chrome/pull/42#issuecomment-754027598 will work with Mocha v7 and forward, but not Mocha v6 and before.

Please Describe Your Changes

Addresses https://github.com/shellscape/mocha-chrome/pull/42#issuecomment-754027598 to fix the updated mocha option from colors (wrong) to color.

This adds a peerDependencies entry in package.json for "mocha": ">= 7.0.0" to represent the requirement of a mocha version that supports the color option.

[ppg]

@shellscape This PR addresses https://github.com/shellscape/mocha-chrome/pull/42#issuecomment-754027598 for Mocha v8 and forward support. Per another comment on that PR would it be possible to get this merged and cut into a release?