Update: add fixer for no-extra-boolean-cast

[not-an-aardvark]

What is the purpose of this pull request? (put an "X" next to item)

[ ] Documentation update
[ ] Bug fix (template)
[ ] New rule (template)
[ ] Changes an existing rule (template)
[x] Add autofixing to a rule
[ ] Add a CLI option
[ ] Add something to the core
[ ] Other, please explain:

What changes did you make? (Give an overview)

This adds a fixer for no-extra-boolean-cast.

if (!!foo);
if (Boolean(bar));
Boolean(!!baz);

// gets fixed to:

if (foo);
if (bar);
Boolean(baz);

Is there anything you'd like reviewers to focus on?

We should double-check that removing parens (e.g. Boolean(bar) --> bar) cannot cause a syntax error.

[mention-bot]

@not-an-aardvark, thanks for your PR! By analyzing the history of the files in this pull request, we identified @vitorbal, @btmills and @Met48 to be potential reviewers.

[eslintbot]

LGTM

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[not-an-aardvark]

I think the "check the status of your PR" page is broken with the new CLA; it just displays the CLA again rather than the status of the PR.

[ilyavolodin]

@not-an-aardvark You should've gotten an email yesterday, but we all need to re-sign CLA due to change with jQuery Foundation -> Linux Foundation

[mysticatea]

LGTM, thank you!