bug(core): a/an indefinite article flagger should allow both before words starting with h followed by a vowel

[hippietrail]

Describe the bug
Many people are of the opinion that "an" should be used before words such as "hotel". Even though I'm not one of these people we should respect their preference.

To Reproduce
Steps to reproduce the behavior:

1. Type "An historical mistake"
2. See "An" flagged with the advice "Incorrect indefinite article"

Expected behavior

1. For now we should not change the advice to something like "Are you sure you want to use 'an' before 'hotel'?"
2. We could also just allow either article before words like 'hotel', 'history', etc.
3. Best would be to have a configurable preference and flag 'an hotel' for some users and 'a hotel' for others.
4. We could also check for consistency, to make sure the same document/repo is not allowing both.

Screenshots

Platform
harper-cli

Additional context
Add any other context about the problem here.