add ChapterFrame type for CHAP frames

[cnt0]

Add CHAP frames parser according to id3v2 documentation. It recognizes only one TIT2 embedded subframe and treats it like a title, which is enough to parse titles added by ffmpeg (example from ffmpeg documentation).

There's also one issue: this parser uses 2 functions, writeFrame and parseFrameHeader, with synchSafe parameter. From what I see there's no way to correctly determine its value when parsing subframe.

[n10v]

Hello @cnt0! Thank you for your PR, but the implementation is not quite correct. As it said in documentation, there could be many embedded subframes in CHAP. The main goal of this library is not a cooperation of ffmpeg, but correct full implementation of id3 spec.

And also tests lack, that is very important.