[WIP] signalingmessage callback を追加する

[voluntas]

This pull request introduces enhancements to the signaling message handling in the Sora SDK. The key changes include adding a new event type for signaling messages, updating related imports and method calls, and ensuring proper logging and event creation for signaling messages.

Enhancements to signaling message handling:

• examples/sendonly/main.mts: Added SignalingMessageEvent type to imports, bound signalingmessage event to onsignalingmessage method, and implemented the onsignalingmessage method to log signaling messages. [1] [2] [3]

• packages/sdk/src/base.ts: Added SIGNALING_MESSAGE_TYPE_CONNECT to imports, replaced createSignalingMessage with createConnectSignalingMessage, and added signalingmessage callback to handle signaling message events. [1] [2] [3] [4] [5]

Updates to type definitions and utilities:

• packages/sdk/src/types.ts: Added signalingmessage callback to Callbacks type and updated SignalingMessageEvent interface to include transportType. [1] [2]

• packages/sdk/src/utils.ts: Added createSignalingMessageEvent utility function and updated imports to include new types and functions. [1] [2]

Minor import adjustments:

• packages/sdk/src/sora.ts: Added SignalingMessageEvent to imports and exports. [1] [2]