gpu: add CommandBuffer, Queue.submit

Signed-off-by: Stephen Gutekanst <stephen@hexops.com>

gpu/src/CommandBuffer.zig

@@ -0,0 +1,25 @@
+const CommandBuffer = @This();
+
+/// The type erased pointer to the CommandBuffer implementation
+/// Equal to c.WGPUCommandBuffer for NativeInstance.
+ptr: *anyopaque,
+vtable: *const VTable,
+
+pub const VTable = struct {
+    reference: fn (ptr: *anyopaque) void,
+    release: fn (ptr: *anyopaque) void,
+};
+
+pub inline fn reference(buf: CommandBuffer) void {
+    buf.vtable.reference(buf.ptr);
+}
+
+pub inline fn release(buf: CommandBuffer) void {
+    buf.vtable.release(buf.ptr);
+}
+
+test "syntax" {
+    _ = VTable;
+    _ = reference;
+    _ = release;
+}