Change check to fail on sound file not ogg

[Fris0uman]

Part of #29

Change the python script slightly so that it fails if the added sound files are not .ogg

tests failed where expected in #50

[dseguin]

Sorry, I just realized that I missed a key piece of functionality here:

diff --git a/tools/validate_unreferenced_sndfile.py b/tools/validate_unreferenced_sndfile.py
index 609b42e..e96a6e3 100755
--- a/tools/validate_unreferenced_sndfile.py
+++ b/tools/validate_unreferenced_sndfile.py
@@ -11,6 +11,13 @@ args.add_argument("fmt", action="store", help="escapes output if set to GHA")
 args_dict = vars(args.parse_args())
 
 
+txt_exts = {
+    ".json",
+    ".txt",
+    ".md"
+}
+
+
 def gha_escape(msg: str) -> str:
     msg = msg.replace("%", "%25")
     msg = msg.replace("\r", "%0D")
@@ -105,6 +112,11 @@ for root, dirs, filenames in os.walk(args_dict["dir"]):
                 retval = 1
             if not check_credits(shortpath):
                 retval = 1
+        elif ext[1].lower() not in txt_exts:
+            printout("Unrecognized file extension \"{}\" for file \"{}\".  "
+                     "Sound files expected in OGG format."
+                     .format(ext[1], filename), 2)
+            retval = 1
 
 if at_least_one == False:
     printout("No sound files processed", 2)

Without this, non-ogg files will be silently ignored