Add no-ui-in-app rule

[Espate]

Resolves #77

[illright]

Hi, thanks for taking a hand at it! I looked over the PR, looks solid, great job. One thing I'd like to add to it is to mention in the rationale of the rule that a valid use case for having a UI segment in App is for applications that only have a single page. They are rare, but they deserve a mention.

Also I noticed a couple of grammatical errors in the rationale, could you please run it through a spell checker like https://languagetool.org/?

[Espate]

Hi, thanks for taking a hand at it! I looked over the PR, looks solid, great job. One thing I'd like to add to it is to mention in the rationale of the rule that a valid use case for having a UI segment in App is for applications that only have a single page. They are rare, but they deserve a mention.

Hi, will update this part.

Also I noticed a couple of grammatical errors in the rationale, could you please run it through a spell checker like https://languagetool.org/?

Could you please point me out where exactly the errors are? I used the tool you referred to, and it didn't reveal any issues, at least in the free plan.

[illright]

I played around with the rationale a bit more, let me know if that sounds okay. If so, then it's ready to merge! Thanks again :)

[Espate]

I played around with the rationale a bit more, let me know if that sounds okay. If so, then it's ready to merge! Thanks again :)

Sure, it works for me too. Thanks!