LibWeb/WebGL2: Implement bufferData with offset and length

Author: https://github.com/Lubrsi
Commit: 18ea91715b
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/2943
Reviewed-by: https://github.com/kalenikaliaksandr

Libraries/LibWeb/WebIDL/Buffers.h

@@ -27,6 +27,7 @@ public:
     virtual ~BufferableObjectBase() override = default;
 
     u32 byte_length() const;
+    u32 element_size() const;
 
     GC::Ref<JS::Object> raw_object();
     GC::Ref<JS::Object const> raw_object() const { return const_cast<BufferableObjectBase&>(*this).raw_object(); }