docs: add 'Importing Sounds'

docs/importing_resources/importing_sounds.rst

@@ -1,2 +1,18 @@
+================
 Importing Sounds
 ================
+
+Crown supports importing both short sound effects and longer music tracks.
+Importing any supported audio file produces a ``.sound`` resource in the
+project alongside the original audio file.
+
+Audio streaming
+===============
+
+During project compilation Crown inspects the audio file and chooses an
+appropriate processing strategy:
+
+* Short sound effects are typically preloaded into memory so playback can
+  start with no delay.
+* Long music tracks use the original file compression and are streamed in at
+  runtime to reduce memory usage.