Better indicate position of additional docs on page

On wide screens, the position of the documentation (how-to and reference guide)
is at same level as #it's-your-data.-keep-it-that-way.

So the jump due to anchor link makes it seem like we're taken to top aka
main content. Indicate that links are to the left so reader doesn't recurse.

README.md

@@ -81,8 +81,8 @@ borgmatic is powered by [Borg Backup](https://www.borgbackup.org/).
 Your first step is to [install and configure
 borgmatic](https://torsion.org/borgmatic/docs/how-to/set-up-backups/).
 
-For additional documentation, check out the links above for <a
-href="https://torsion.org/borgmatic/#documentation">borgmatic how-to and
+For additional documentation, check out the links above (left panel on wide screens)
+for <a href="https://torsion.org/borgmatic/#documentation">borgmatic how-to and
 reference guides</a>.