Add sdl2glue to vendor:wgpu package + triangle example

vendor/wgpu/sdl2glue/glue_darwin.odin

@@ -0,0 +1,25 @@
+package wgpu_sdl2_glue
+
+import    "vendor:sdl2"
+import    "vendor:wgpu"
+import CA "vendor:darwin/QuartzCore"
+import NS "core:sys/darwin/Foundation"
+
+GetSurface :: proc(instance: wgpu.Instance, window: ^sdl2.Window) -> wgpu.Surface {
+    window_info: sdl2.SysWMinfo 
+    sdl2.GetWindowWMInfo(window, &window_info)
+    ns_window := cast(^NS.Window)window_info.info.cocoa.window
+    metal_layer := CA.MetalLayer_layer()
+    ns_window->contentView()->setLayer(metal_layer)
+    return wgpu.InstanceCreateSurface(
+        instance,
+        &wgpu.SurfaceDescriptor{
+			nextInChain = &wgpu.SurfaceDescriptorFromMetalLayer{
+				chain = wgpu.ChainedStruct{
+					sType = .SurfaceDescriptorFromMetalLayer,
+				},
+				layer = rawptr(metal_layer),
+			},
+		},
+    )
+}