wip: enable to work with form-control-sm and form-control-lg

[ttskch]

#fixes #40

Unfortunately, it's impossible to make small or large .select2-container--open element because it's totally independent from <select> tag which has class form-control-sm or form-control-lg.

So container can be made smaller or larger but search bar and selector cannot 🤔

[ttskch]

If we want to make smaller or larger also .select2-container--open element, we have to use javascript. To be honest I don't wont to do that 🤔