Minor issues with mobile version

[Patol75]

I identified two issues when loading the g-adopt website on a mobile Web browser:

• The navigation column does not default to the content index on the landing page;
• The return-home button is hidden in the navigation column; it should be accessible on the page.

[angus-g]

Point 1 is kind of tricky to address. I don't really understand how the whole interaction model is implemented in Material for MkDocs, and there are no customisations available out of the box. We could change the TOC to separate the home and about pages, but that makes the top navigation tab even busier...

Point 2 is addressed in https://github.com/g-adopt/g-adopt.github.io/tree/angus-g/header-link

[Patol75]

Could the content of About be moved to Documentation under a tab called Rationale?

[drhodrid]

I can't remember what we decided on this at the dev meeting, but at the AARC this week, a number of people used a QR code to visit our webpage (via their mobile) and clearly struggled a little with navigation. We probably need to address this in the near future.