feat: Shard#kill method (#2454)

* add shard#kill method

* docs consistency

src/sharding/Shard.js

@@ -112,16 +112,23 @@ class Shard extends EventEmitter {
     return this.process;
   }
 
+  /**
+   * Kills this shard.
+   */
+  kill() {
+    this.process.removeListener('exit', this._exitListener);
+    this.process.kill();
+    this._handleExit(false);
+  }
+
   /**
    * Kills and restarts the shard's process.
    * @param {number} [delay=500] How long to wait between killing the process and restarting it (in milliseconds)
    * @param {boolean} [waitForReady=true] Whether to wait until the {@link Client} has become ready before resolving
    * @returns {Promise<ChildProcess>}
    */
   async respawn(delay = 500, waitForReady = true) {
-    this.process.removeListener('exit', this._exitListener);
-    this.process.kill();
-    this._handleExit(false);
+    this.kill();
     if (delay > 0) await Util.delayFor(delay);
     return this.spawn(waitForReady);
   }