add decoder

[DougLau]

It would be great to have a decoder which could be used to filter/test mvt files.

[DaviTeodoro]

Any plans to do so?

[DougLau]

Not in the immediate future, unfortunately. PRs welcome, though.

[nyurik]

There is a MVT reader implementation in geozero - https://github.com/georust/geozero/tree/main/geozero/src/mvt