Make the Contributing Guide more visible

[jeromecambon]

Currently, the Contribution Guide is not well visible to the doc contributors. and is often not read.

The idea is to make it visible close to the "Edit this page" button, so that the contributors can obviously see (and read!) it. Here is the proposed design:

The first (pencil) icon will have a "Edit this page" tooltip, and point (as before) on the github editor. The second icon (info) will have a "How to contribute" tooltip and point on the Contribution Guide.

The design will also adapt to the light and dark themes.

As a reminder, here is the current "Edit button" look and feel

[tbouffard]

Sources of inspiration: https://docs.fedoraproject.org/en-US/fedora/f30/

[tbouffard]

@jeromecambon we could also add a button as in the fedora docs to link to the git history of the source file. This will be a first iteration for https://github.com/bonitasoft/bonita-documentation-site/issues/435

"Page history" button in the Fedora docs

[jeromecambon]

Didn't find so far how to get an URL for the history. Trying to find how Fedora doc is doing this. See: https://gitlab.com/fedora/docs/docs-website/ui-bundle/-/blob/main/src/partials/toolbar.hbs

[tbouffard]

an URL for the history.

the toolbar.hbs is using edit2var to transform the edit.urland generate the url to the commits history of the file see https://gitlab.com/fedora/docs/docs-website/ui-bundle/-/blob/main/src/helpers/edit2var.js