Add a user view

We don't have a design for this yet, so safe to keep it simple, just a new route and the basic information without paying too much attention to styling

Needs api support for:

• getting/refreshing the account https://docs.joinmastodon.org/api/rest/accounts/#get-api-v1-accounts-id
• and its relationships https://docs.joinmastodon.org/api/rest/accounts/#get-api-v1-accounts-relationships
• statuses of a user (also with the only_media flag) https://docs.joinmastodon.org/api/rest/accounts/#get-api-v1-accounts-id-statuses