Enhance Syntax highlighter

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• Setup own color theme (@ffd8 can yo do that)
• Update _config.yml with line numbers (@fabianmoronzirfas )
• Add alternating row colors and smaller leading (scss @fabianmoronzirfas )
• Add Robot+Mono (scss @fabianmoronzirfas )

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Took a look at some options mostly concerning the alternating row colors.
On the example you send me you re using highlight.js which does all kind of JS magick to create the lines. The end result is an ol > li setup for creating the alternating row colors.

The options in jekyll are all based on the markdown parser. Rouge (which we are currently using, commonmark or redcarpet). As far as I could see none has alternating row colors build in.

Means for the alternating colors we would have to do some magick with the possible markdown parsers or switch to hightlight.js

I would not want to switch to highlight.js

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The other things can be done