docs: Added *more* examples to README.md.

examples/streams-audio.nu

@@ -0,0 +1,10 @@
+#!/usr/bin/env nu
+
+use ../ffprobe ["main" "streams audio"];
+
+# Extract the audio streams from a video
+def main [] {
+  echo "> ffprobe https://sample-videos.com/video321/mp4/720/big_buck_bunny_720p_1mb.mp4 | streams audio"
+  ffprobe $'($env.FILE_PWD)/videos/sample-videos.com/video321/mp4/720/big_buck_bunny_720p_1mb.mp4'
+  | streams audio
+}