added discord rpc (#1178)

* added discord rpc

* linting issues

* Revert "linting issues"

This reverts commit 55f4e39506.

* fix clang-format issues

* removed wrong rpc submodule

* added correct rpc submodule

* Moved cmake instructions to correct files.

* added minor suggestions from pr

* Added an option to enable/disable RPC, added rpc to emulator.cpp making it work on nonqt builds

* typo & minor stuff

* Changed getInstance implementation with Singleton class.

* Update discord_rpc_handler.cpp

discord id

* fixed ci clangformat errors

---------

Co-authored-by: georgemoralis <giorgosmrls@gmail.com>

.gitmodules

@@ -94,4 +94,7 @@
 [submodule "externals/pugixml"]
 	path = externals/pugixml
 	url = https://github.com/zeux/pugixml.git
-	shallow = true
+	shallow = true
+[submodule "externals/discord-rpc"]
+	path = externals/discord-rpc
+	url = https://github.com/shadps4-emu/ext-discord-rpc