Use mvt-fixtures for testing valid/invalid vector tiles?

Nobody has claimed this yet.

👋 we've recently released [mvt-fixtures](https://github.com/mapbox/mvt-fixtures) as an attempt to centralize test fixtures for decoding mvt buffers. I'd love to see vector-tile-js using this library at some point in the future. Presumably mvt-fixtures doesn't contain every unit-test fixture required for this library, so I'll work on updates there to make sure there is feature parity before working on a branch in this project.

mvt-fixtures comes with a method for testing _all_ fixtures relatively quickly - `.each()` and this would allow us to run vector-tile-js through every fixture plus test whether it should decode the fixture successfully or not. [Example in the README](https://github.com/mapbox/mvt-fixtures/#javascript-usage).

It also comes with a selection of real-world tiles that can be used for benchmarks and [tests like this one](https://github.com/mapbox/vector-tile-js/blob/master/test/parse.test.js#L34-L35).

I'll plan on being point here for prototyping what this can look like, but if anyone has thoughts or concerns please feel free to raise them here!

cc @mapbox/core-tech @jfirebaugh @lbud @mollymerp @mourner @anandthakker @lucaswoj

Start with the mvt-fixtures README's JavaScript usage and the existing real-world tile coverage in test/parse.test.js. Review which fixtures vector-tile-js currently requires and compare them with mvt-fixtures before deciding what integration is needed. Done means the relevant valid, invalid, and real-world tile tests use the centralized fixtures without losing required coverage.

Written by the indexing model from the issue text.