4.21.0 - build: Automate copyright year management - meson-build: Function check cleanup - build: Fix function checks - poppler-thumbnailer: Only use embedded thumbnail if resolution suffices - meson-build: Use SPDX license expression - meson-build: Update debug/optimization flag management - autotools-build: Add missing gtkdocentities.ent.in to EXTRA_DIST - Add meson build - ffmpeg-thumbnailer: Bump ffmpeg version and drop CHECK_VERSION - Set up GNU symbol visibility - tumbler: Don't install tumbler-marshal.h - Translation Updates: Albanian, Romanian, Slovak