Please add a change log

[gcv]

CSTParser is a fine piece of software, but, as noted in #56, does not have a public API. Right now, for people building tools on top of it, this can cause headaches as it's difficult to track what changed. I maintain an Emacs IDE for Julia which uses CSTParser, for example (https://github.com/gcv/julia-snail), and the API changed at some point from 2.5.0 to 3.1.0 in just a couple of months.

Until CSTParser has a backwards-compatible API, it would be great to at least know what changed from version to version. General change log principles described here: https://keepachangelog.com/en/1.0.0/

[o314]

The script https://github.com/JuliaLang/julia/blob/master/doc/NEWS-update.jl of Julia itself can be of interest for that purpose too