docs: Add/normalize .toString() docs on all classes (#2042)

* docs: Add/normalize .toString() examples on all classes

* docs: Remove exclamation point on ClientApplication#toString example

* docs: Normalize .toString() descriptions on all classes

* Use "returns" instead of "concatenates"

src/structures/Role.js

@@ -332,8 +332,11 @@ class Role extends Base {
   }
 
   /**
-   * When concatenated with a string, this automatically concatenates the role mention rather than the Role object.
+   * When concatenated with a string, this automatically returns the role's mention instead of the Role object.
    * @returns {string}
+   * @example
+   * // Logs: Role: <@&123456789012345678>
+   * console.log(`Role: ${role}`);
    */
   toString() {
     if (this.id === this.guild.id) return '@everyone';