Fix MOD_ICON's misleading config comments (#759)

* Fix MOD_ICON's misleading config comments

* lowercase folder stuff and fix grammar

* Update ModConfigWarning.hx

---------

Co-authored-by: Ralty <78720179+Raltyro@users.noreply.github.com>

source/funkin/editors/ModConfigWarning.hx

@@ -22,10 +22,11 @@ API_VERSION=1
 DOWNLOAD_LINK="YOUR MOD PAGE LINK HERE"
 
 # Not supported yet
-;MOD_ICON64="path/to/icon64.png"
-;MOD_ICON32="path/to/icon32.png"
-;MOD_ICON16="path/to/icon16.png"
-ICON="path/to/icon.png"
+;MOD_ICON64="path/to/icon64"
+;MOD_ICON32="path/to/icon32"
+;MOD_ICON16="path/to/icon16"
+# The path starts in "your-mod/images/", do not add image extension.
+ICON="path/to/icon"
 
 [Flags] # This section doesn\'t apply any prefix.
 DISABLE_WARNING_SCREEN=true
@@ -84,4 +85,4 @@ LOGO_TEXT=""
 		], false);
 		openSubState(substate);
 	}
-}
+}