Refresh Data Import Guide

[fulghum]

The Importing Data Guide could use a quick refresh.

The import best practices sections is hidden at the bottom of the page, making it difficult for customers to find and it could also use some more detail (e.g. explain how to turn off foreign key checks, explain how to use dolt verify constraints after turning them back on). Some of the recent import perf enhancements might have some updates in the doc, too (e.g. do we still need to recommending minimizing blob usage now that their import perf is much more reasonable?).

Putting linkable navigation by use case (e.g. importing a MySQL dump) up at the top would help, too (we have some use cases bulleted, but not linked, so makes navigating the doc harder).