ruby : output format (#3237)

* Fix a typo

* Don't allocate output string unless needed

* Add methods to output SRT and WebVTT

* Add tests for output methods

* Make constants for output private

* Add signatures for output methods

* Add document on output methods

* Fix method name: Segment#speaker_next_turn? -> #speacker_turn_next?

* Add Whisper::Segment#descotruct_keys

* Add test for Whisper::Context#descotruct_keys

* Add signature of Whisper::Segment#deconstruct_keys

* Use parentheses to suppress warning

* Update date

bindings/ruby/README.md

@@ -162,6 +162,32 @@ Whisper::Params.new(
 
 For details on VAD, see [whisper.cpp's README](https://github.com/ggml-org/whisper.cpp?tab=readme-ov-file#voice-activity-detection-vad).
 
+### Output ###
+
+whispercpp supports SRT and WebVTT output:
+
+```ruby
+puts whisper.transcribe("path/to/audio.wav", Whisper::Params.new).to_webvtt
+# =>
+WEBVTT
+
+1
+00:00:00.000 --> 00:00:03.860
+ My thought I have nobody by a beauty and will as you poured.
+
+2
+00:00:03.860 --> 00:00:09.840
+ Mr. Rochester is sub in that so-don't find simplest, and devoted about, to let might in
+
+3
+00:00:09.840 --> 00:00:09.940
+ a
+
+```
+
+You may call `#to_srt`, too
+
+
 API
 ---
 
@@ -196,7 +222,7 @@ whisper
       ed: format_time(segment.end_time),
       text: segment.text
     }
-    line << " (speaker turned)" if segment.speaker_next_turn?
+    line << " (speaker turned)" if segment.speaker_turn_next?
     puts line
   end
 
@@ -212,7 +238,7 @@ params.on_new_segment do |segment|
     ed: format_time(segment.end_time),
     text: segment.text
   }
-  line << " (speaker turned)" if segment.speaker_next_turn?
+  line << " (speaker turned)" if segment.speaker_turn_next?
   puts line
 end