Returns a list of `GtkTextTag` that are toggled on or off at this point.
toggled_on is true, the list contains tags that are toggled on. If a tag is toggled on at
this, then some non-empty range of characters following this has that tag
applied to it. If a tag is toggled off, then some non-empty range following this does not have the tag applied
true to get toggled-on tags
tags toggled at this point