Write Dimension Field When Encoding

[mawi510]

Problem

The encoder only writes the dimension field if dim != 2, otherwise, no dimension is written when encoded. While this works fine for the JS decoder (because it forces dim = 2 when decoding), this can lead to decoding issues when decoding outside of the JS decoder. I recently ran into this issue and upon searching this and the pygeobuf repo, I posted a similar explanation of the issue, including:

1. Decoding in the Python Implementation of Geobuf: Pygeobuf
2. Decoding from PostGIS

Proposed Solution

When encoding, allow dimensions to be an argument that a user can insert, otherwise, default to 2 rather than not writing the dimension field. This way all encoded data defaults to a 2D space (unless otherwise noted), which makes the geobuf data easier to decode outside the JS decoder.