Adds compatibility with the indentLine plugin

Fixes #48

Working for me, tried with and without the indentLine plugin, so these lines shouldn't introduce any breakage.

Needed to do it a little different from what I initially said in #48, of course, as indentLine has to do something to disable and reenable itself.
Therefore a dependency to the IndentLinesToggle command is introduced. We could add a try-catch clause to make sure nothing breaks, but I guess no matter how much that little indentLine plugin changes, this command will stay, so we should be all good.