Add invalidateSize

I use Leaflet maps in a resizable container in my Blazor app. I needed the ability to call invalidateSize() when the container changes size so that leaflet will use the proper dimensions when knowing when to ask for more tiles.

Not sure if you are taking pull requests or not, but thought I would pass it on.

Hi, thank you for your contribution. We implement BlazorMaps very closely connected to original Leaflet library, please see how invalidateSize is implemented in Leaflet. Can you correct your changes have one of parameters in a method, ZoomPanOptions or bool?

https://leafletjs.com/reference-1.7.1.html#map-methods-for-modifying-map-state

Also please change your target branch to develop branch

It would be great to have this PR added in. I was looking for this on the weekend. We just hacked it in via javascript, but a Blazor command would be better.