TGB Dual and GW cores added

Two new cores have been added!

https://store.steampowered.com/app/1227450/RetroArch__GW/

https://store.steampowered.com/app/2010120/RetroArch__TGB_Dual/

You can download these cores either from within RetroArch Steam by going to Manage Cores, or by simply downloading them for free from Steam.

If you'd like to learn more about these two cores, you can refer to more information on our Documentation Center site.

Documentation for GW core can be found here. Documentation for the TGB Dual core can be found here.

There are now 37 cores available in total for RetroArch Steam.