Highlight mouseover elements (WIP)

[trafficonese]

This is a follow-up from #53 and includes #74 .

Although everything seems to work fine, I am seeing Problems in Visual Studio:

Property 'glify' does not exist on type 'typeof import("c:/../Leaflet.glify/node_modules/@types/leaflet/index")'

I also had to include import L from 'leaflet'; for lines/shapes/points, as otherwise I would have had 3 additional problems.

I am not sure why this happens or how it is done correctly. I tried different approaches without success. Using new Lines instead of L.glify.lines fixes the problem in VS but it doesn't work and throws several webGL warnings and an error in the console:

Uncaught Error: shader variable color not found

I hope someone can shed some light on these problems.