[FEAT] More documentation in the Manpage

[ValdezFOmar]

Wanted features:

• Include all the available options, currently only a subset (compared to fastfetch --help) is actually listed.
• Include the information from running fastfetch -h <option> for all options.
• Explain/give examples of the structure of the config file, accepted values for options, how to change common things, etc.
• Include the JSON Schema found in the github wiki.

Motivation:

When I want to read thorough documentation for a tool I look at the manpage (as many others might do). I expect to find more information in man foo than running foo --help. Right now, some of the info is available in the manpage, more is in fastfetch --help and other is in the github wiki.

Having all the documentation in the manpage would be beneficial because:

1. There would be a centralized place to look for the documentation, without needing to look at external resources or having to run multiple commands (running fastfetch -h <option> constantly is not very ergonomic).
2. Users can leverage the features of the program they use to read manpages to search for specific topics of their interest more easily.

[CarterLi]

The man page file was contributed by community, but I'm not familiar the man page file syntax.

Any contribution is welcome.

[ValdezFOmar]

Neofetch used help2man to generate a manpage using output from --help. Another option is to use pandoc to convert from any format (eg. markdown) to a manpage.

I think that pandoc would be best because then you can convert the JSON schema to a manpage too.