v1.0.0 - Stable

This marks the first stable release of arc, meaning that from this point on, the project follows semantic versioning, and no breaking changes will happen (until an eventual 2.0).

• Add loops. Loops can be used to repeatedly call a given coroutine function with a specific interval or cron set.
• Add concurrency limiters. Concurrency limiters can be used to prevent users from invoking a command that already has a specific amount of instances running.
• Add arc.StartedEvent and arc.StoppingEvent to gateway clients to enable managing lifecycle via events.
• Fix command groups always being republished when command syncing.

In additon to these changes, the documentation got a major refresh, adding & extending guides where needed.