firefox-wrapper: add missing gstreamer plugins

These GStreamer plugins are required for H264 <video> tag support in Firefox.
firefox-wrapper: use gstreamer hook
Update Powertop: 2.6.1 -> 2.7
Merge pull request #5251 from ts468/powertop

Update Powertop: 2.6.1 -> 2.7
firefox-wrapper: add gstreamer plugins for h264 video support

These plugins are required by firefox for the h264 support in HTML5 <video> tags.
installer tests: don't rely on swap.target until systemd bug is fixed
nixos/systemd: ignore null environment options
nixos: add fleet module
k2pdfopt: update and fix build
Add the Dina font
clearlooks-phenix: Fix the Meta Description
Merge pull request #5256 from prikhi/add-dina-font

Add the Dina font
Merge pull request #5257 from prikhi/fix-clearlooks-phenix

clearlooks-phenix: Fix the Meta Description
Merge pull request #5255 from offlinehacker/nixos/fleet

nixos: add fleet module
Add suckless.org sinit for experiments