feat: Add new isRTL function

[susnux]

• Resolves: Provide an isRTL method #84

Add isRTL to check whether a given, or the current, language is right-to-left read.
Use cases would be e.g. nextcloud/server#31420 or nextcloud/forms#1637

🧪 Testcases included

[ahangarha]

Thanks for your work on this feature.

It seems you use the locale used by the person creating the form. This is not ideal. I might use English but I want to create a form in RTL (or the opposite).

There are two proposals:

1. Add an option to set the direction of the form (this can get its default value from the locale of the creator of the form). This is flexible but not yet not preferred.
2. Make any user-generated field/content to set the direction automatically using dir="auto". Here, we need to also fix any styles related to left|right to use logical styles (like text-aligh: start or padding-inline-start|end,...

I prefer the last one. It is very flexible and no magic logic is required to be implemented.

[susnux]

@ahangarha Thank you for your feedback, I think it should be on the forms issue.
As this particular pull request is not about forms or any front end part, but just adds a requested function to determine if a given language is a RTL language or not.

Lets discuss the forms part there :)

And it is not about the creator of the form, but this feature would use the current users locale / language, as Nextcloud let you configure a language other than your user agents language which overrides the user agent.

[ahangarha]

Oh! Sorry for mistaking the PR.
Well done

[ShGKme]

Why do we check for locale and not only the language here?

[susnux]

Language is never falsy but at least "en"

[susnux]

Could be removed

[ShGKme]

Thanks!