0.4.0

• Emoji support(implemented by @AWolf81 in #374)
• Make checkboxes clickable(implemented by @pfftdammitchris in #402)
• Improve UI
  • Show sync status in sidebar
  • Improve context menu in sidebar
  • Refine UI coloring(It's not done yet. It will be improved more in v0.5.0)
  • Start replacing custom icons with material design icons
• Use dark theme UI by default
• Use material-darker theme for code editor and code fences by default
• Discard broken tutorial and import tab(They will be back soon)