Allow to set border and text color per event

[mikekreeki]

Thanks for this project btw, awesome job!!

Having per-event color for events is lovely. However, many will benefit from the ability to set border/text color for events as well. One can do it via a theme, but that would be a single color used globally. There's currently no way to have, for example, a light red event background and a slightly darker red border color around i with even darker text, as shown here (the border is not very visible as the color difference is subtle on the screenshot, but it is there):