adding geoportail france provider (new try)

[gcebelieu]

This PR adds Geoportail France provider to leaflet-providers. Same goal as @fionnh previous unmerged PR (#279). The code comes from Mediawiki Extension:Maps latest evolution (ProfessionalWiki/Maps#437) which uses leaflet-providers as a dependency.

[brunob]

Hi and thanks for the patch, two points :

• there are some typos in README file
• protocol relative urls are not used anymaore here, tou should always use https if it's available, and http if there is no https.

[gcebelieu]

Hi and thanks for paying attention to this PR. Corrections done.

[brunob]

"De rien" & thx for the fixes, GTM @jieter ?

[jieter]

@gcebelieu @brunob is is a good idea to add this API key? I have an api key for HERE here, it gets a lot of views, regularly over 10M/month. That is without being in the default distribution, only views from the preview.
I didn't read into this provider, but they might not like that.

[brunob]

@gcebelieu can tell us more about it since he seems to work for IGN which is linked to the provider ;)

[gcebelieu]

@brunob, indeed :)
@jieter, thanks for the warning. This api key is a demonstration key that give access to a little part of Geoportail resources. We will see how much traffic will come from that publication but in any cases the geoportail platform is fitted to handle more than 10M WMTS hits a month.
So its ok to use this api key.

[jieter]

👍