[AppStream] AppStream 0.15.6 released!

[Matthias Klumpp]

Hello!
This is very likely the last release of AppStream for this year,
featuring more bugfixes and some refinements.
Enjoy the holidays and the new release!

Tarballs available here:
https://www.freedesktop.org/software/appstream/releases/

Cheers,
    Matthias

Version 0.15.6
~~~~~~~~~~~~~~
Released: 2022-12-22

Features:
 * qt: Add API for ContentRating descriptions and ratingIds
 * Add some coccinelle semantic patches for common style issues
 * compose: Allow building without SVG support (for bootstrap only)
 * validator: Check for nodes that are text nodes even though they shouldn't be
 * validator: Extend validation for custom tag
 * validator: Improve Screenshot validation

Specification:
 * docs: Fix typos in <extends> documentation

Bugfixes:
 * validator: internat: Don't allow bandwidth_mbitps when value is offline-only
 * validator: Fix timestamp validation
 * validator: Allow release descriptions to start with punctuation
 * compose: Only add no-metainfo tag if component isn't already ignored
 * compose: Show better error in AscImage if compose was build without rsvg
 * Add a hack to clarify proper PtrArray element ownership for language bindings
 * qt: Port away from deprecated QDateTime API
 * qt: Deprecate Component::requires
 * qt: Fix warning
 * qt: Fix stringListToCharArray and Pool::componentsByCategories
 * qt: Port away from deprecated foreach
 * as-review: Add a typedef for property enums
 * as-review: Install properties at once rather than individually
 * as-review: Specify G_PARAM_STATIC_STRINGS for properties
 * as-review: Emit GObject::notify on property value changes
 * as-review: Add missing property for as_review_{get,set}_priority()
 * ascli: fix NULL pointer dereference

Miscellaneous:
 * docs: Split releases specification into its own section
 * style: Make code easier to read by using helper macros in all places
 * Make some compiler warnings fatal unconditionally

Contributors:
 Aleix Pol, JakobDev, Matthias Klumpp, Nicolas Fella, Philip Withnall,
 r-ricci, Will Thompson