Feat/manpage

[ajinkyagawali1]

fixes #1704

Prerequisite checklist

• Read the contribution guidelines regarding submitting new changes to the project;
• Tested your changes against relevant architectures and platforms;
• Ran make fmt on your commit series before opening this PR;
• Updated relevant documentation.

Description of changes

Added a man page for the Kraft CLI based on the kraft --help option. Also modified the installer script to install the man page on Linux Systems.

[nderjung]

Hi @ajinkyagawali1, thanks for your contribution!

I recommend having a look at the gendocs tool we have internally which currently generates documentation pages in markdown format.

I fear with your solution that this becomes difficult to maintain since it is a static representation of the main help screen as of today.

Please re-review the #1704 as it has the requirements for solving the issue which is to modify this program to output in valid man-page format. You can use cobra's man_docs.go (godoc) program for reference utility methods.