add GoogleMapsCompatible TMS to match GDAL TMS

[vincentsarago]

ref developmentseed/titiler#431 (comment)

There are small differences between GDAL GoogleMapsCompatible and the WebMercatorQuad TMS defined by morecantile. It all comes down to the value of the earth HALF_CIRCUMFERENCE defined as

# GDAL
https://github.com/OSGeo/gdal/blob/35c07b18316b4b6d238f6d60b82c31e25662ad27/gcore/tilematrixset.cpp#L79
>> 20037508.342789244

# Morecantile 
https://github.com/developmentseed/morecantile/blob/master/morecantile/data/WebMercatorQuad.json#L9
>> 20037508.3427892

I'm not sure I want to modify the WebMercatorQuad so IMO, adding a new TMS seems to be the better solution.

Note: we need a better name than GoogleMapsCompatible

[vincentsarago]

This is in fact not needed for rio-tiler nor titiler because rio-tiler is smart enough to handle small rounding errors