Suggested instance for registration

**Is your feature request related to a problem? Please describe.**
When registering as a new user in Voyager, it always defaults to lemmy.zip. This can be a problem because it means that this instance grows too big, while other instances dont get many new users. Additionally it doesnt account for user's location or language.

**Describe the solution you'd like**
[join-lemmy.org](https://join-lemmy.org) has a new API [api/v1/instances/suggested](https://join-lemmy.org/api/v1/instances/suggested) to retrieve suggested instances, which are currently generated based on the user's IP location. See https://github.com/LemmyNet/joinlemmy-site/pull/586 for details and the [data file](https://github.com/LemmyNet/joinlemmy-site/blob/main/src/shared/data/instances-definitions.ts#L13) for list of suggestions.

Additionally there is an endpoint [api/v1/instances/all](https://join-lemmy.org/api/v1/instances/all) which includes all instances listed on join-lemmy.org, to show your own instance selection. The API endpoints are not in use yet, so if necessary they can be adjusted based on your feedback. The list of suggested instances can also be changed (discussion in https://github.com/LemmyNet/joinlemmy-site/issues/545).

When a user wants to register, it should look something like this, using the instance returned from api/v1/instances/suggested:

> **Register on lemmus.org**
> - Username
> - Email
> - Password
> - Other inputs like registration application, captcha, enable nsfw etc
> [Register] [Browse Other Instances]

**Describe alternatives you've considered**
- Keep the current behaviour with a single, hardcoded instance
- Implement a similar logic directly in Voyager (list of suggested instances which are selected based on some criteria)

**Additional context**