Minor changes

• Improve headerbar buttons on hover state
• Improve budgie panel appearance
• KDE: Add sddm theme
• KDE: Add sddm theme to dependencies
• Improve disabled buttons style
• KDE: Improve splashscreen
• KDE: Add solid variant to kvantum
• Gnome-shell: Add visual separation to osd-panel related to #69
• Gnome-shell: Remove unnecessary shadow in some widgets

Patches

• Fix headerbar button color in backdrop state
• Fix sidebar transition issue #52
• Fix invisible text on treeview progressbar
• Gnome-shell: Fix gnome 3.36 issues #62
• Gnome-shell: Fix unstyled notwork list widget on v3.36
• Gnome-shell: Fix popover issues on v3.36