[LTP] [RFC PATCH 1/1] doc: Split test-writing-guidelines

[Xie Ziyao]

>>> https://github.com/pevik/ltp/wiki/Test-Writing-Guidelines
>>> https://github.com/pevik/ltp/wiki/C-Test-API
> 
> Seems we have a similar guideline "c-test-tutorial-simple.txt",
> maybe better to combine them together?
> 
>>> https://github.com/pevik/ltp/wiki/Shell-Test-API
> 
> Forgot to mention, with the increased number of docs, do you think it
> necessary to create an index for including all documents in a sort?
+1

I think this is a good proposal.

Kind regards,
Ziyao