i18n support

[cb0s]

What do you think about language support by the front-end?
Is it planned and if so, when will this be implemented? :)
If it is not planned what do you think about translations in general?

I know this is more relevant for the single subprojects however the core could already provide general functionality.

[fussel178]

Great question!
I personally thought about this for a while and searched around a little.

We only really need the internationalisation in the telestion-client-common package.
The telestion-client-core package only set up, arranges and renders children and app settings and provides the developer APIs to create PSCs.

After a short search, I found two interesting solutions:

1. The built-in solution from Adobe React Aria (especially the I18nProvider component and associated hooks).
2. The full stack internationalisation i18next with React support.

I personally tend towards the built-in solution from Adobe because it's easy to set up, well documented and has a good integration with the existing project dependencies and structure (usage in the CommonWrapper component).

@pklaschka What do you think?

[pklaschka]

I've used the react-intl package before. I'm not entirely sure if one's better, more complete, etc. Let's maybe take a look at the different options and see what we want to use.

I18n, of course, is a large topic, so whatever we choose, it should probably be powerful enough so we don't have to switch later down the line.