mods: add main menu credits

Should work well with upcoming custom background.

config/isxander-main-menu-credits.json

@@ -0,0 +1,10 @@
+{
+	"main_menu": {
+		"top_left": [
+			{
+				"text": "Resistance's Base (@Eneri_777)",
+				"color": "light_purple"
+			}
+		]
+	}
+}