adding a usage file as an example

bindings/ruby/USAGE.md

@@ -0,0 +1,12 @@
+# Ruby Guide
+
+We expose Whisper::Context and Whisper::Params.  The Context object can be used to transcribe.
+Parameters can be set on the Params object to customize how the transcription is generated.
+
+```
+  whisper = Whisper::Context.new('ggml-base.en.bin')
+  params  = Whisper::Params.new
+  whisper.transcribe('jfk.wav', params) {|text|
+    assert_match /ask not what your country can do for you, ask what you can do for your country/, text
+  }
+```