Use WebVTT.build for chapters vtt file

src/invidious/videos/chapters.cr

@@ -49,37 +49,9 @@ module Invidious::Videos::Chapters
 
   # Converts an array of Chapter objects to a webvtt file
   def self.chapters_to_vtt(chapters : Array(Chapter))
-    vtt = String.build do |vtt|
+    vtt = WebVTT.build do |build|
-      vtt << <<-END_VTT
-      WEBVTT
-
-
-      END_VTT
-
-      # Taken from Invidious::Videos::Caption.timedtext_to_vtt()
       chapters.each do |chapter|
-        start_time = chapter.start_ms.milliseconds
+        build.cue(chapter.start_ms.milliseconds, chapter.end_ms.milliseconds, chapter.title)
-        end_time = chapter.end_ms.milliseconds
-
-        # start_time
-        vtt << start_time.hours.to_s.rjust(2, '0')
-        vtt << ':' << start_time.minutes.to_s.rjust(2, '0')
-        vtt << ':' << start_time.seconds.to_s.rjust(2, '0')
-        vtt << '.' << start_time.milliseconds.to_s.rjust(3, '0')
-
-        vtt << " --> "
-
-        # end_time
-        vtt << end_time.hours.to_s.rjust(2, '0')
-        vtt << ':' << end_time.minutes.to_s.rjust(2, '0')
-        vtt << ':' << end_time.seconds.to_s.rjust(2, '0')
-        vtt << '.' << end_time.milliseconds.to_s.rjust(3, '0')
-
-        vtt << "\n"
-        vtt << chapter.title
-
-        vtt << "\n"
-        vtt << "\n"
       end
     end
   end