Fit width/height of the generated map by bbox mapOption

[samuel-litzler]

Request Feature :

Fit perfectly the size of width / height of the generated map with the bbox mapOption.

explanation with this bbox (blue feature) : [4.8514292, 45.7795070, 4.8535790, 45.7779198]

width and height set to 450 :

width and height set to 500:

You can see that there is padding around bbox(blue feature) -> because of zoom level(integer), here zoom is between 18 and 19 so it takes 18 to see the blue feature.

I dont know how works your code / externals librairies (sharp) you used but do you thing there is a way to perfectly fit with BBOX ?

(request initialy comes from #84 )