Split view design

What's Changed

• build: replace appstream-utils with appstreamcli, according to th… by @Rirusha in #39
• Added Bulgarian translations by @twlvnn in #41
• Move inline css to separate css file by @TanmayPatil105 in #42
• Improve dark mode css by @TanmayPatil105 in #43
• Move all tool specific sidebar code/ui into related tool by @Nokse22 in #45
• Improved app design
• Fixed bug when monospace font is not present
• Added a menu entry to open the directory where custom palettes are stored

New Contributors

• @Rirusha made their first contribution in #39
• @twlvnn made their first contribution in #41
• @TanmayPatil105 made their first contribution in #42

Full Changelog: v0.3.4...v0.4.0