Force black text for search input

[ericholscher]

Fixes #420

[ericholscher]

This lints fine for me locally 🤷

-> npm run lint

> @readthedocs/addons@0.30.0 lint
> prettier --check .

Checking formatting...
All matched files use Prettier code style!

[ericholscher]

I updated my hooks and got this, but then pre-commit changes it back 🙃

prettier.................................................................Failed
- hook id: prettier
- files were modified by this hook

[agjohnson]

You probably have an old version of prettier installed and pre-commit/circleci are using the later release. npm install should fix discrepancies with linting like this, this solved what was probably the same issue for me.

[humitos]

You should probably do the same work for the "X" shown at the right of the input field. It's currently white as well.