Display human-readable license names

Currently the license tile for Free applications appears to display the raw SPDX identifier from the appdata. Here for example the otherwise human-readable text includes the string "GPL-3.0-or-later":

It might be nice to use a human-readable name for the license. libappstream does not appear to provide this, though the data does exist, e.g. https://github.com/spdx/license-list-data/blob/master/json/licenses.json

libappstream does provide a function to get a URL for more details about the license: https://www.freedesktop.org/software/appstream/docs/api/appstream-as-spdx.html#as-get-license-url

One issue here may be translations, since the SPDX database does not translate license names. In the example above, the human-readable name for the license available is “GNU General Public License v3.0 or later”, which might look strange when the surrounding text is not in English. (However the SPDX codes already include English words.)

Adding the full English name, and a link to the license details, might look like this: