Add Leaflet maxZoom to configParameters

[glughi]

What this PR does

Related to #7280

Add "leafletMaxZoom" to configParameters so that the maxZoom of the Leaflet viewer can be changed.

Test me

How should reviewers test this? (Hint: If you want to provide a test catalog item, create a Gist of its catalog JSON, add its url and your branch name to this url: http://ci.terria.io/<branch name>/#clean&<raw url of your gist> , and then paste that in the body of this PR)

Checklist

• There are unit tests to verify my changes are correct or unit tests aren't applicable (if so, write quick reason why unit tests don't exist)
• I've updated relevant documentation in doc/.
• I've updated CHANGES.md with what I changed.
• I've provided instructions in the PR description on how to test this PR.

[CLAassistant]

All committers have signed the CLA.

[na9da]

Thanks for the change @glughi.

I have made a couple of comments.

[na9da]

I think, because this is a map level config, it is better to pass it to the Map instance created here:

terriajs/lib/Models/Leaflet.ts

Lines 149 to 155 in 676d1d8

	this.map = L.map(container, {
	zoomControl: false,
	attributionControl: false,
	zoomSnap: 1, // Change to 0.2 for incremental zoom when Chrome fixes canvas scaling gaps
	preferCanvas: true,
	worldCopyJump: false
	}).setView([-28.5, 135], 5);

[glughi]

Hi, as you can read in the documentation of Leaflet (https://leafletjs.com/reference.html#map-maxzoom) the MapOptions.maxZoom property has no default limitations. The GridLayerOptions.maxZoom property is set to 18 by default, so it is the one to change so that zoom greater than 18 can be used.