Feature/add bbox url precision

[ketourneau]

Description

When we try to use a custom WMS source (omniscale provider) we got some mistake if the coordinate in BBOX url is rounded.

Motivation and Context

We would like to set custom precision of BBOX passed in url to solve our problem.
In our case if bbox precision is 9 it's work.

sourceMap = new itowns.WMSSource({
    url: `https://maps.omniscale.net/v2/${omniscaleKey}/style.default/map`,
    name: "osm",
    format: "image/png",
    crs: "EPSG:2154",
    extent: extent,
    version: '1.1.0',
    bboxUrlPrecision: 9
});

Screenshots

bboxUrlPrecision: 2

bboxUrlPrecision: 9

[Desplandis]

Hi and thanks for your PR! =)
It seems that our defaults are overfitting on IGN datasets, we may have to change them later (don't hesitate to open an issue if the defaults are causing issues with other datasets).

[ketourneau]

For the time we don't have any overfitting with IGN ortho data, only with omniscale Open Street Map.
I applied your code review, thanks for the review.

[Desplandis]

Sounds good to me!
I saw the implementation of both mapbox and openlayers and they use numbers directly without truncating them, it may have been a fix for some IGN datasets, I will look into it!