- Implemented audio support with Video.js.

What changed:
Added uploaded/direct audio playback paths in 
[index.php](/Users/tyemeclifford/Documents/GH/mediaplayer/index.php) and 
[embed.php](/Users/tyemeclifford/Documents/GH/mediaplayer/embed.php).
Added common audio upload support: MP3, M4A, AAC, WAV, FLAC, OGG, OGA, 
OPUS.
Added waveform poster generation for uploaded audio via ffmpeg, stored 
like normal thumbnails under media/thumbs/.
Updated add/edit forms to accept media files, not just video files.
Added audio-friendly labels like Audio, 320kbps, 256kbps, 128kbps.
Updated docs and changelog.

admin/settings.php

@@ -132,7 +132,7 @@ render_head('Settings — Admin', '
       </a>
       <a href="add.php">
         <svg width="14" height="14" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2"><circle cx="12" cy="12" r="10"/><line x1="12" y1="8" x2="12" y2="16"/><line x1="8" y1="12" x2="16" y2="12"/></svg>
-        Add Video
+        Add Media
       </a>
       <a href="youtube_import.php">
         <svg width="14" height="14" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2"><path d="M22.54 6.42a2.78 2.78 0 00-1.95-2C18.88 4 12 4 12 4s-6.88 0-8.59.46a2.78 2.78 0 00-1.95 2A29 29 0 001 12a29 29 0 00.46 5.58 2.78 2.78 0 001.95 2C5.12 20 12 20 12 20s6.88 0 8.59-.46a2.78 2.78 0 001.95-2A29 29 0 0023 12a29 29 0 00-.46-5.58z"/><polygon points="10,15 15,12 10,9"/></svg>