Decide new theme or create one for help pages

[magicDGS]

For example:

• https://github.com/aksakalli/jekyll-doc-theme
• https://github.com/DigitalMindCH/docster-jekyll-theme

Without a live demo (should check):

• https://github.com/amzn/jekyll-doc-project
• https://github.com/ovh-ux/ovh-jekyll-doc-theme

Relates with #423 and #506