Information text for the new widgets

[romain-fontugne]

This pull request add information text for most of the widgets of the new website. And some related improvements.

Description

• info text for the widgets.
• restructure of the IXP page
• fix the title for some charts

Motivation and Context

This is part of the polishing to deploy the new version of the website.

How Has This Been Tested?

I went through a lot of the pages to check that I didn't break things.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.