Add “developer tools” tag

[Wuzzy2]

Please add a tag for mods that are devloper tools because mods like schemedit, ltool and perlin_explorer don’t fit into any of the provided categories so far.

I define a “developer tool” as anything that is primarily designed to help mod and game developers develop their things.

[rubenwardy]

done

[Wuzzy2]

Nice. I've added the tag to 13 things.

https://content.minetest.net/packages/?page=1&tag=developer_tools