Update README.md

- Minor changes, copyright year, 3DGE became EDGE v2, link to EDGE v2 repo for attribution (at least for this file).

README.md

@@ -4,13 +4,13 @@
 
 ## GZDoom is a modder-friendly OpenGL and Vulkan source port based on the DOOM engine
 
-Copyright (c) 1998-2019 ZDoom + GZDoom teams, and contributors
+Copyright (c) 1998-2021 ZDoom + GZDoom teams, and contributors
 
 Doom Source (c) 1997 id Software, Raven Software, and contributors
 
 Please see license files for individual contributor licenses
 
-Special thanks to Coraline of the 3DGE team for allowing us to use her README.md as a template for this one.
+Special thanks to Coraline of the EDGE team for allowing us to use her [README.md](https://github.com/3dfxdev/EDGE/blob/master/README.md) as a template for this one.
 
 ### Licensed under the GPL v3
 ##### https://www.gnu.org/licenses/quick-guide-gplv3.en.html