Add documentation for FileName sniff

[Nic-Sevic]

Related to #1722

• docs/Files/FileNameStandard.xml

[rodrigoprimo]

Thanks for your contribution, @Nic-Sevic! Usually, a <standard> and <code_comparison> block should be created for each of the error/warnings generated by the sniff, but there are some exceptions. Did you intentionally combine everything in a single <standard> and <code_comparison> pair? Without thinking too much about it, I'm more inclined to think that it would be better to separate the error/warning messages.

I just noticed that what I shared above is not mentioned in #1722, so there is a big change you were not aware of that (cc @jrfnl in case we should add this information in the issue description or maybe link to https://github.com/PHPCSStandards/PHP_CodeSniffer/blob/master/.github/CONTRIBUTING.md#writing-sniff-documentation). That is my bad.

[rodrigoprimo]

@Nic-Sevic, I was just wondering if you'll have a chance to finish this off in the near future. It would be great if this PR could be included in the next WPCS release.

If you haven't got time or lost interest, please let us know and we'll see if we can find someone to take over. Thanks!

[rodrigoprimo]

@Nic-Sevic, please let us know within a week if you are still interested in finishing this PR. If we don't hear back from you, we will presume you don't have time, and we will see if we can find someone else to take over and finish it. Thanks for your work so far!