Align GeographyType values with shapely.GeometryType

[benbovy]

Replaces #90 (automatically closed by deleting target branch != main).
Closes #88.

[jorisvandenbossche]

I don't have a strong opinion about whether it is better to align, or better to just have our own enum (or align with WKB values, which is 1-7).
Whichever we choose, it should always be recommended to compare with the enum and not with a direct integer, and if you follow that then the actual number does not matter too much.

[benbovy]

Whichever we choose, it should always be recommended to compare with the enum and not with a direct integer, and if you follow that then the actual number does not matter too much.

I agree, however there's no easy way to support that here (#51 (comment)) so we have to stick with comparing values for now (hence this PR and #88).

That said, aligning with WKB is a good point (I didn't know about that) and probably better than aligning with shapely? I'll leave this PR and #88 open and move on with the 0.1.0 release.