Add a how-to page to explain the recommended way to update this guide

[glemieux]

Is your feature request related to a problem? Please describe. There is no page explaining how to update this document and fates-docs. This should be added to help users engage with improving the documentation.

Describe the solution you'd like A how-to page explaining the update and pull request workflow.

Describe alternatives you've considered Put this in the Tutorials section instead?

Additional context None

[glemieux]

This should probably include a style guide as well.