Expand mod.conf with additional meta information (author, version, copyright, etc.)

Problem

While mod.conf has seen minor improvement in recent years, in particular by #6243 to contain the mod dependencies and description, I believe there is still value in further expanding its scope with additional meta information about mods, particularly for use by the Content DB as well as to anticipate the future creation of game configuration and management tools.

Solutions

My original proposal cited below entailed the addition of four more fields, aside from the existing name, description, and depends.

https://forum.minetest.net/viewtopic.php?p=305622#p305622

For compatibility reasons name should really be title. I also suggest adding an icon field (that refers to an image be located in the /textures subdirectory), a license field (that is the name of the license, not the full text), and a website field (that is a URL to the forum fopic or GitHub repository). Here's a revised example:

name = my_farming
description = a great mod for useful farming tools
depends = default, farming
icon = my_farming_icon.png
title = My Farming Mod
version = 1.0 beta
website = https://www.example.com/
author = supermodder
license = MIT
copyright = Copyright (c) 2017, supermodder

Incidentally, I discovered that @rubenwardy had suggested something similar in #2201, even though that issue was closed and only a couple of fields were actually incorporated into the official documentation. So in some respects, I'd like to resurrect that discussion and see if we can settle on a truly futureproof "standard" of sorts for mod.conf.