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(1) → integrate rainbow into the
      Colours gem, at the least the core functionality from:
        http://www.rubydoc.info/gems/rainbow/2.1.0

require 'rainbow'; x = Rainbow("hola!").blue.bright.underline; pp x; ''
"\e[34m\e[1m\e[4mhola!\e[0m"
# ^^^

    e Rainbow("hola!").blue.bright.underline
    e Colours("hola!").blue.bright.underline

Colours('hi').red
^^^ as a first step enable this.
and then document it as well.

This works fairly well now, since as of November 2022. 

We may have to still check whether we implement all of it
or not.
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(2) → in colours. fix the italic part. The problem is that the default
      colour is not restored correctly so. We may need to simplify
      this eventually.
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