Print cli usage of hugo gen chromastyles alongside css

[diwasrimal]

When I was playing around generating chromastyles, I forgot what style I was using during generation. hugo gen chromastyles [flags] [args] doesn't print any information about how the styles were generated, which would be beneficial to know.

This pull request prints a comment above the generated css styles showing the cli usage during the chromastyles generation.

Now it ouputs like

$ ./hugo gen chromastyles --style=catppuccin-macchiato
/* Generated using: hugo gen chromastyles --style=catppuccin-macchiato */

/* Background */ .bg { color:#cad3f5;background-color:#24273a; }
/* PreWrapper */ .chroma { color:#cad3f5;background-color:#24273a; }
...

[CLAassistant]

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