[Request] Disable dates

[seras42]

Hey, you have made a pretty great date-picker for svelte. It has this very nice minimalist quality feeling to it that is hard to come by.

I was wondering if there is a possibility to mark specific dates with a different colors in DatePicker? Or an ability to only display enabled or disabled dates? I am working on a appointment registration system and it would be nice to mark available dates different color or only show those dates.

I have seen that there was some pull request in relation to something similar but i guess nothing came of that? #92

I have no experience in developing svelte packages but maybe i could figure something out and make a pull request for an ability to color specific dates different colors in the DatePicker?

Thank you for your time, and the work that you put in this project.

[probablykasper]

Feel free to submit a PR implementing isDisabledDate. About coloring I'm not so sure, it sounds a bit too specific