Initial implementation of GPUShaderModule

Added WebIDL bindings for `GPUShaderModule`.
Implemented the `createShaderModule` function of `GPUDevice`.

components/script/dom/webidls/GPUShaderModule.webidl

@@ -0,0 +1,15 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+// https://gpuweb.github.io/gpuweb/#gpushadermodule
+[Exposed=(Window, DedicatedWorker), Serializable, Pref="dom.webgpu.enabled"]
+interface GPUShaderModule {
+};
+GPUShaderModule includes GPUObjectBase;
+
+typedef (Uint32Array or DOMString) GPUShaderCode;
+
+dictionary GPUShaderModuleDescriptor : GPUObjectDescriptorBase {
+    required GPUShaderCode code;
+};