goose doc: Sharing sessions service and how to share sessions

This pull request updates the documentation for managing Goose sessions, focusing on improving clarity and adding new functionality for session sharing. Key changes include updating instructions for starting and resuming sessions, introducing a comprehensive section on sharing sessions, and minor adjustments to the structure of the guide.

Updates to session management instructions:

Updated the description for starting a new session in Goose Desktop to reflect the change from the "three dots" icon to the "gear" icon. ([documentation/docs/guides/managing-goose-sessions.mdL19-R19](diffhunk://#diff-08b4b977d065693949daba778a60368ed3033df53b958ca3a73405f1ceb95c34L19-R19))
Modified the CLI command for resuming sessions, changing the placeholder <name> to <n> for consistency. ([documentation/docs/guides/managing-goose-sessions.mdL99-R99](diffhunk://#diff-08b4b977d065693949daba778a60368ed3033df53b958ca3a73405f1ceb95c34L99-R99))

New functionality: Session sharing

Added a detailed section on enabling and using session sharing in Goose Desktop, including setup instructions, sharing sessions, and viewing shared sessions. This includes requirements for implementing a session sharing service and links to the API reference documentation. ([documentation/docs/guides/managing-goose-sessions.mdL232-R293](diffhunk://#diff-08b4b977d065693949daba778a60368ed3033df53b958ca3a73405f1ceb95c34L232-R293))

Structural adjustments:

Reorganized the guide by moving the "Search Within Sessions" section to follow the new "Share Sessions" section. ([documentation/docs/guides/managing-goose-sessions.mdL232-R293](diffhunk://#diff-08b4b977d065693949daba778a60368ed3033df53b958ca3a73405f1ceb95c34L232-R293))