Feat sdiff initial with parser

[GunterSchmidt]

This is a first version of sdiff.

It implements the a new, fully working parser for the arg options, which also can easily be implemented for the other utils.
While it does not implement any functionality to compare the files, the parser is finished (pending bugs). This allows any developer to start working on the compare functionality with the prefilled Param struct having the options set.

The 'sdiff' seems to work largely identical to 'diff', with a different layout in the output. Code sharing should be possible.

The parser is written generically so it can be used in all diffutils tools. I already have a version for cmp as well.
After discarding clap as tool, as the requirements are very individual and would require extensive tweaking of the clap functionality.

There are a number of cases where the current parser does not yield the same results as GNU cmp, for instance 'cmp file_1 file_2 -bln50KiB'.

Since 'sdiff' does not exist yet, this is pure additional code. It also contains a help and version text, which needs to be finalized after discussion so no copyright infringement is taking place. I already reformulated some of the text.

I originally wanted to implement 'clap', but after some investigation I found the requirements of diffutils highly individual and it would require extensive tweaking of the clap functionality.

Relates to #16 and #97.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 0.00%. Comparing base (6f082c6) to head (d57b0c5).

Additional details and impacted files

@@     Coverage Diff     @@
##   main   #187   +/-   ##
===========================
===========================

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[GunterSchmidt]

Merged sdiff logic from PR #159.

This is now a good option parser and has basic sdiff compare functionality. This is a good base for further development.

I suggest to merge #159 first to give @zxvfc credit. I then can update my PR as the changes are small.

[sylvestre]

it is now conflicting, could you please fix that ? thanks