Add docs for the servers sub-module of groups

src/groups/mod.rs

@@ -1,16 +1,16 @@
 //! Payphone-specific code. All features like calls and moderation go here.
-//! 
+//!
 //! Sub-modules in this module usually follow the same structure:
-//! 
+//!
 //! - A `mod.rs` file exporting the public API of the sub-module.
 //! - A `commands.rs` file containing the command definitions.
 //! - A `embeds.rs` file containing embed-generating functions for those commands.
 //! - A `events.rs` file containing event handlers related to the features the sub-module covers.
 //! - Any additional modules the sub-module may specifically require.
-//! 
+//!
 //! An example of extra modules not listed above is the [`calls::moderation`] module, which
 //! includes the tools for parsing messages and detecting rule breakings in them.
-//! 
+//!
 //! > *Note that not all sub-modules have commands, nor they all have event listeners, etc. Each of
 //! > them only defines the modules they need.*