[BUG] Adopt Swift 6

[miklselsoe]

Describe the bug
For Swift 6 conformance, it is important to know what types are sendable and which are not as well as actor declaration. Please adopt Swift 6 for this project and declare Sendable conformance as well as which types are constrained to the main actor.

[nauaros]

Hi @miklselsoe,

We're actively working to address all the Swift 6 conformance issues. Please, pay attention to the notes in the following releases. Thank you!