Add Man-Page for Unix-Like Systems about pyscenedetect

Hi,

I am trying to write the man page(If i may).

I have a few questions, which are as follows:

1. Should the man page be a separate file?
   If yes, maintaining multiple documents (manpage.md, readme.md and usage.md)
   with some common information would be tedious.

2. Can the information required to form manpage.md be extracted from existing
   documents/code?

This is my first effort to make an OSS contribution.
I am not sure if this is a good first issue to pick up.
Please guide.

[Breakthrough]

Absolutely, feel free! (Make sure to include all the CLI parameters if you do so, can also get it from v0.5-beta-1 by calling help all). There is just one last feature (the -n flag on the save-images command) and documentation that is being updated before the release of v0.5, so some of the documentation may be expanded.

In response to your questions:

1. No if possible, but I'm not sure if that is... One option is to call scenedetect help all and use that as the man scenedetect text, which I am more than open to. If this needs to be saved as an actual manpage file and updated as part of the release process, that's okay with me so long as it can be automated.

2. Absolutely, yes! Also again, not sure if it needs to be a .md file - all I know is I want to be able to run man scenedetect on Linux in order to close this issue 😄

The hardest part of the issue would be distributing it in a way that lets you do man scenedetect on a Linux system. I'm not sure how to do that, or if it's even possible (may require writing a shell script to be executed afterwards in the setup.py?)...

That being said, please feel free to take on the issue if you think you can complete it - have confidence, and thank you for your interest in PySceneDetect! 🎥