Add option to disable excludeDatesPicker

[jonasbadstuebner]

I'm handling date exclusion differently; I don't need the picker.
So I would love to have a configuration option that lets me omit this picker.

I'll provide a PR.

[jonasbadstuebner]

I just noticed there is already an option for this.
But it doesn't follow the style using RRuleGeneratorConfig. Let me know if you want me to open a PR to migrate this to the config.

[jonasbadstuebner]

I'd be happy to use the flag I just found though, so it's up to you - it's your package after all.