🔨 add powershell script to split stereo sound files into 2 mono files

- see

package-scripts/dev/split-ogg-stereo-to-mono.ps1

@@ -0,0 +1,7 @@
+# https://stackoverflow.com/a/47905308/13789724
+$files = Get-ChildItem ".\resourcepack\assets\omega-flowey\sounds\"
+foreach ($f in $files) {
+  if ($(ffprobe -i $f.fullname -show_entries stream=channels -select_streams a:0 -of compact=p=0:nk=1 -v 0) -ne 2) { continue }
+  ffmpeg -i $f.fullname -map_channel 0.0.0 "$($f.directoryname)/$($f.basename)_channel_0.ogg" -map_channel 0.0.1 "$($f.directoryname)/$($f.basename)_channel_1.ogg"
+  remove-item $f.fullname
+}