Add new activity options

[benjammin4dayz]

Describe the feature you'd like

This is a multi-part feature request because I think the changes are closely related and small enough to not warrant three separate issues:

1. Add optional URL fields for state, details, large_image, small_image
2. Add an option to choose the ActivityType (e.g. Playing, Listening, Watching, Competing)
3. Add an option to choose the StatusDisplayType (e.g. app name, state, details)

Why is this feature needed?

It will improve the user's ability to express themselves and provide a more thorough example for developers to reference in their own implementations.

Additional context

Some or all changes may require the discord-rich-presence crate to be updated from v0.2.5 to v1.0.0

1. The new URL fields are state_url, details_url (ref), assets.large_url, assets.small_url (ref)

2. The activity type can be set by passing the activity::ActivityType enum to the activity::Activity::activity_type method

3. The status display type can be set by passing the activity::StatusDisplayType enum to the activity::Activity::status_display_type method

vionya/discord-rich-presence#52
vionya/discord-rich-presence#54
discord/discord-api-docs#7674