Add documentation for discord/sanitizing.rs module and add a few more characters to escape in SanitizeDiscordMarkdown

src/discord/sanitizing.rs

@@ -1,4 +1,15 @@
+//! Utilities for sanitizing Discord messages (removing markdown from user input).
+
+/// Escapes Discord markdown in a string.
 pub trait SanitizeDiscordMarkdown {
+    /// Escapes Discord markdown in a string.
+    ///
+    /// Arguments:
+    /// * `hard` - If `false`, it'll only escape mentions and pings. Otherwise, it'll also escape
+    ///   generic markdown like headers and code blocks.
+    ///
+    /// Returns:
+    /// [`String`] - The sanitized string.
     fn sanitize(&self, hard: bool) -> String;
 }
 
@@ -14,7 +25,8 @@ where
 
             for ch in input.chars() {
                 match ch {
-                    '\\' | '*' | '_' | '~' | '`' | '>' | '<' | '|' | '#' => {
+                    '\\' | '*' | '_' | '~' | '`' | '>' | '<' | '|' | '#' | '[' | ']' | '/'
+                    | '(' | ')' => {
                         escaped.push('\\');
                         escaped.push(ch);
                     }