games: real recorded foley for cards and chips, synth for the rest

The card and chip sounds never convinced as oscillators, so they're now
CC0 recordings (Kenney's casino pack) under /static/audio/casino, embedded
in the binary. Six names (card, deal, flip, shuffle, chip, sweep) play
several rotating takes with a little pitch jitter; everything melodic stays
synthesised. PeteSFX's API is unchanged and synthesis is the fallback while
an ogg is still decoding, so no caller changed and the table is never silent.

internal/web/static/audio/casino/LICENSE.txt

@@ -0,0 +1,21 @@
+	
+
+	Casino Audio
+
+	by  Kenney Vleugels (Kenney.nl)
+
+			------------------------------
+
+	License (Creative Commons Zero, CC0)
+	http://creativecommons.org/publicdomain/zero/1.0/
+
+	You may use these assets in personal and commercial projects.
+	Credit (Kenney or www.kenney.nl) would be nice but is not mandatory.
+
+			------------------------------
+
+	Donate:   http://support.kenney.nl
+	Request:  http://request.kenney.nl
+
+	Follow on Twitter for updates:
+	@KenneyNL