Fix #1107 (optimized version)

[ForgottenGensym]

See #1107, this is a more optimized version than just an isInfinite check, because it specifically checks only for positive infinity (the edge case here).

This adds two new Kernel.Basics JS functions (accessible via the associated Basics Elm functions):
isPositiveInfinity and isNegativeInfinity. These are useful for more than just this fix as well.

[github-actions]

Thanks for suggesting these code changes. To set expectations:

• Pull requests are reviewed in batches, so it can take some time to get a response.
• Smaller pull requests are easier to review. To fix nine typos, nine specific issues will always go faster than one big one. Learn why here.
• Reviewers may not know as much as you about certain situations, so add links to supporting evidence for important claims, especially regarding standards for CSS, HTTP, URI, etc.

Finally, please be patient with the core team. They are trying their best with limited resources.