[strict-boolean-expressions] Add ignore-rhs option

[glen-84]

Repro

{
  "rules": {
    "@typescript-eslint/strict-boolean-expressions": "error"
  }
}

// OR
function valueOrDefault(a?: string) {
    return a || "the default";
}

// AND
const condition = true;
condition && valueOrDefault();

Expected Result

No error (with an option or options).

Actual Result

Error: Unexpected non-boolean in conditional. (twice)

Additional Info

TSLint has an ignore-rhs option (see documentation).

It might make sense to also consider this issue.

#698 would also be required (at least for the first example).

Other links:

• TSLint orginal issue
• TSLint duplicate issue
• TSLint PR

Versions

package	version
@typescript-eslint/eslint-plugin	1.13.0
@typescript-eslint/parser	1.13.0
TypeScript	3.4.5
ESLint	6.1.0
node	10.16.0
npm	6.9.0

[bradzacher]

#691

[JamesHenry]

The PR has been merged