add module docs

Author: jhgg

crates/rust-analyzer/src/handlers/notification.rs

@@ -1,3 +1,6 @@
+//! This module is responsible for implementing handlers for Language Server
+//! Protocol. This module specifically handles notifications.
+
 use std::{ops::Deref, sync::Arc};
 
 use itertools::Itertools;

crates/rust-analyzer/src/handlers/request.rs

@@ -1,3 +1,6 @@
+//! This module is responsible for implementing handlers for Language Server
+//! Protocol. This module specifically handles requests.
+
 use std::{
     io::Write as _,
     process::{self, Stdio},