feat(shared): api call to get /api/user

feat(schema, shared, api): move all types to shared, separate schema
 * schema is now stored in a separate crate to avoid dependency cycles
 * added note in README.md about handling unwraps

feat(shared): relocate types, add gamestate consts

feat(shared): extract_cookie macro

feat(client, server, shared): new login/register

feat!(client, shared): move api calls to shared, dep shuffle,
and remove connection check stage