3rd-party integrations in Jellyflix

[jdk-21]

Jellyflix itself is a third-party client, and I believe third-party integrations can significantly enhance Jellyflix. To determine whether a third-party integration should be allowed in Jellyflix, I intend to establish some guidelines that projects must adhere to. As these guidelines are not yet finalized, I welcome your feedback before they are added to the contributing guidelines.

Planned requirements:

The project must:

• Be popular within the Jellyfin community.
• Have an open-source license.
• Be actively maintained.
• Provide either a Dart API or an OpenAPI spec.

The integration must:

• Offer seamless integration; added features should blend seamlessly with Jellyflix's existing interface. The integration should be implemented in a way that allows for easy addition and removal of features without disrupting the user experience for those who do not utilize them.
• Receive active support from its maintainers, either by developing the integration themselves or by assisting Jellyflix contributors.
• Comply with relevant App Store guidelines (e.g., Apple, Google, F-Droid).
• Always be optional for the user.

Additionally, first-party Jellyfin features will always be preferred over similar third-party features.