[new rule]: ternary-operator-spacing

[arhontmw]

PR checklist

• Addresses an existing issue: #0000
• New feature, bugfix, or enhancement
  • Includes tests
• Documentation update

Overview of change:

New rule, which determines whether a space is required before and/or after question and colon tokens in ternary conditional operator

[palantirtech]

Thanks for your interest in palantir/tslint, @arhontmw! Before we can accept your pull request, you need to sign our contributor license agreement - just visit https://cla.palantir.com/ and follow the instructions. Once you sign, I'll automatically update this pull request.

[johnwiseheart]

Hey @arhontmw, is there an issue where this change is discussed? Currently most (if not all) of whitespace linting is done by the whitespace rule and it would be good to have a discussion about the pros and cons of separating that rule into several more specific rules. If there is not an issue, feel free to create one.

[arhontmw]

Added issue #4122

[JoshuaKGoldberg]

Per discussion in #4122, and more broadly the upcoming deprecation of TSLint (#4534), closing this issue for housekeeping. @arhontmw you can always publish this rule in a standalone npm package if you'd like to see it used!