geoparquet.md: refer to OGC spec for WKB instead of ISO

[rouault]

There's actually a OGC spec that describes WKB, and is in-line with ISO 13249-3 (SQL/MM Part 3: Spatial), except that the OGC spec doesn't define the CircularString, CompoundCurve and CurvePolygon classes but reserve the same number as SQL/MM Part 3.

[alasarr]

@jorisvandenbossche as you wrote that part. Are you ok with this PR?

[jorisvandenbossche]

Thanks! It's indeed good to refer to an official spec.
I would maybe still keep a mention of "ISO" as alternative name (or a reference to the ISO standard) for people who know it by that name?

[rouault]

I would maybe still keep a mention of "ISO" as alternative name (or a reference to the ISO standard) for people who know it by that name?

link to the corresponding ISO SQL MM / Part 3 language added

[jorisvandenbossche]

Thanks!