sokol_gfx_imgui.h: add missing ETC2 pixel format names

util/sokol_gfx_imgui.h

@@ -1001,6 +1001,9 @@ _SOKOL_PRIVATE const char* _sg_imgui_pixelformat_string(sg_pixel_format fmt) {
         case SG_PIXELFORMAT_PVRTC_RGBA_4BPP: return "SG_PIXELFORMAT_PVRTC_RGBA_4BPP";
         case SG_PIXELFORMAT_ETC2_RGB8: return "SG_PIXELFORMAT_ETC2_RGB8";
         case SG_PIXELFORMAT_ETC2_RGB8A1: return "SG_PIXELFORMAT_ETC2_RGB8A1";
+        case SG_PIXELFORMAT_ETC2_RGBA8: return "SG_PIXELFORMAT_ETC2_RGBA8";
+        case SG_PIXELFORMAT_ETC2_RG11: return "SG_PIXELFORMAT_ETC2_RG11";
+        case SG_PIXELFORMAT_ETC2_RG11SN: return "SG_PIXELFORMAT_ETC2_RG11SN";
         default: return "???";
     }
 }