fix(config loader): deal with config file charset

[hxzhao527]

make sure that config file charset is utf-8, or throw detail to notify.
for #465 [Question] SyntaxError: Parsing JSON at for commitizen config failed

[hxzhao527]

I have resolved the conflict, maybe it is time to merge or close this pr.

[jimthedev]

Thanks for your contribution! This looks good!

[harryparkdotio]

@jimthedev can we revert this, or at least provide a hotfix release which includes is-utf8 as a dependency?

[jimthedev]

@harryparkdotio Revert issued.

[hxzhao527]

It's my mistake.
In my first version, I include the dependency isutf8(not is-utf8) manually. But ci failed me.:joy:
So I check my local node_modules folder, and found is-utf8.
I will add this dependency.