chore(starters): add gatsby-starter-leaflet

[colbyfayock]

Description

• Adds gatsby-starter-leaflet to showcase.
• Adds new category Mapping:Leaflet - the goal is to both provide the top level category of Mapping to encourage more map submissions with a subset of Leaflet, as there are other popular Mapping frameworks available.

[wardpeet]

Let's not create a specific tag for Mapping:Leaflet as it's not widely used.

[colbyfayock]

@wardpeet sure thing, updated it to just Mapping

[wardpeet]

We don't want to add Mapping either 😛. Sorry about this but we don't want to add to many categories to our list. We also need to remove some that shouldn't be there.

[colbyfayock]

fair enough, though I 🤞maybe it'll appear some day. it's an increasingly growing space with a lot of interesting technical work. we're building https://www.element84.com/dr/ on Gatsby for instance :)

removed from both files

[LekoArts]

Thanks 👍