generate: add README about how to create sounds for new languages.

generate/README.markdown

@@ -0,0 +1,22 @@
+How to create sounds for other languages
+========================================
+
+* Record sounds for 0-9 and put them into a directory with language names.
+  Speak fast enough to make sound files small.  Make sure the level of sound is
+  the same as in the provided samples for English (this is important for making
+  captchas harder to break). Same files in 8 KHz 8-bit PCM WAV format.  (To do
+  this in Audacity, set "Project Rate (Hz)" at the lower left corner to 8000,
+  then File > Export, select "Other uncompressed files", click Options...,
+  select "WAV (Microsoft)" for Header, and "Unsigned 8 bit PCM" for Encoding.)
+
+  If you're not sure if your sounds are okay or how to save them properly, just
+  save one of them into any format (MP3 is okay), and send it to me
+  <dmitry@codingrobots.com>. I'll check it, and if it's okay, I'll ask you for
+  other sounds, and process them myself (in this case, you can stop reading.)
+
+* Put 0.wav - 9.wav into the subdirectory with language name (e.g. "ua").
+
+* Open main.go and edit "var langs" on line 21 to include the new directory
+  name.
+
+* make && ./generate