CLI: FX option not documented.

[EatThePath]

I scoured the documentation today trying to find how to specify the output file format in a batch conversion, and found no sign at all of it. I found the -fx option by looking around this issue tracker, and it resolved that issue, but it really ought to be documented somewhere

[ymmikhail]

Thanks, we'll add this option to the documentation

[NPCompress]

The issue has been resolved in current release v4.4