doc: factor-out repetitive documentation

[Totodore]

Motivation

Currently, the documentation for all the operators is duplicated multiple times in the codebase for the different methods in Socket, ConfOperators, BroadcastOperators, and SocketIo. This duplication makes the documentation difficult to maintain, as updates must be made in every instance.

I will also work on improving the documentation style by removing third-person verbs and consistently writing documentation in the imperative mood (e.g., "Get a socket ID" instead of "Gets a socket ID").

Solution

• Factor out the documentation for these functions into external .md files and use #[doc = include_str!("path")] to include the corresponding documentation files.
• Enhance the documentation by adding more examples and establishing stable style guidelines (both visual and grammatical).