Added link to borgbackup list --format docs

I kept searching for this link, so it's time to add it to official docs.

docs/how-to/inspect-your-backups.md

@@ -47,9 +47,10 @@ borgmatic list
 borgmatic info
 ```
 
-(No borgmatic `list` or `info` actions? Try the old-style `--list` or
-`--info`. Or upgrade borgmatic!)
+You can change the output format of `borgmatic list` by specifying your own using `--format $FORMAT`. Refer to the official [borg list --format specs](https://borgbackup.readthedocs.io/en/stable/usage/list.html#) for available options.
 
+*(No borgmatic `list` or `info` actions? Try the old-style `--list` or
+`--info`. Or upgrade borgmatic!)*
 
 ### Searching for a file