Add a page on Internationalization to the docs

[LorisSigrist]

Describe the problem

Internationalization is clearly very important to SvelteKit & the community, as shown by the

• Translations #1274
• i18n brainstorming #553

Despite this, when you currently search "i18n" on kit.svelte.dev you get no results.

IMO, this goes counter to Svelte's "simple questions should have simple answers" ethos.

Describe the proposed solution

Add a Page to the documentation on Internationalization that outlines:

• The current state of development
  • Why SvelteKit does not yet offer i18n out of the box
  • The goals for a first-party i18n solution
  • Where to contribute to the discussion
• Which i18n solutions SvelteKit users can use today

This would give people a quick overview of the state of affairs & give them a starting-off point

Alternatives considered

do nothing

Importance

nice to have

Additional Information

As someone who has built several i18n libraries I obviously place higher importance on i18n than most people. Perhaps others don't place the same importance on i18n & are fine with the current state.