Improve logo and the welcoming page generated by foal createapp

[LoicPoullain]

Issue

The logo and the welcoming page are dull.

Solution and steps

Use brighter colors.

Old logo:

New logo:

Old page:

New logo:

Checklist

• Add/update/check docs.
• Add/update/check tests.
• Update/check the cli generators.

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (v0-6-2@33129ba). Click here to learn what that means.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             v0-6-2     #270   +/-   ##
=========================================
  Coverage          ?   99.77%           
=========================================
  Files             ?       52           
  Lines             ?      909           
  Branches          ?      185           
=========================================
  Hits              ?      907           
  Misses            ?        2           
  Partials          ?        0

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