Encoding about as slow as JSON.stringify

[ghost]

Consider this a companion for #114 to also challenge this claim from the README (and the similar claim from the pbf README):

Very fast encoding and decoding — even faster than native JSON parse/stringify.

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Namely, this is our use-case: maplibre/maplibre-gl-js#106 (comment)

In Chrome, for me, JSON.stringify and geobuf.encode, seem to take about ~200ms each.
I did not try other browsers yet.

(Unfortunately I can't share my actual GeoJSON, but if we decide to move forward with trying to make geobuf work for us, then I'll likely construct a similar test case; our GeoJSON is described in the linked issue though)