Replace setFilter highlighting with new source highlighting

[mattesCZ]

Update "query similar features" example

Much faster way to highlight features proposed in #2492 discussion

[mattesCZ]

The highlighting is not perfect now. Features should be unioned before highlighting. Is it fine to improve the example with dependency on turf-union?

[jfirebaugh]

Thanks for the suggestions, but we'd like to keep this example simple, without external dependencies. We'll look at issues such as #200 and #2443 for further performance improvements.