Fixes units in Python writer default bounds

[daniel-j-h]

When there are no user-provided bounds provided in the writer (as in: min/max_lat/lng_e7 properties) the writer mistakenly defaults to -180,-90,180,90 for these properties.

PMTiles/python/pmtiles/tile.py

Lines 277 to 283 in e1228f5

	min_lon_e7 = h.get("min_lon_e7",-180)
	write_int32(min_lon_e7)
	min_lat_e7 = h.get("min_lat_e7",-90)
	write_int32(min_lat_e7)
	max_lon_e7 = h.get("max_lon_e7",180)
	write_int32(max_lon_e7)
	max_lat_e7 = h.get("max_lat_e7",90)

But these properties need to be multiplied by 10000000 as seen e.g. in this examples and as indicated by the "_e7" postfix

PMTiles/python/examples/create_raster_example.py

Lines 29 to 32 in e1228f5

	"min_lon_e7": int(-180.0 * 10000000),
	"min_lat_e7": int(-85.0 * 10000000),
	"max_lon_e7": int(180.0 * 10000000),
	"max_lat_e7": int(85.0 * 10000000),

Without this fix we were seeing pmtiles with bounds around null island, because the order of magnitude was wrong.

[bdon]

Good catch, thanks!