Implement groups view in sidebar using Vue

[UnniKohonen]

Description of the enhancement

Adding a Vue component for group view in the sidebar.

What new functionalities would the enhancement make possible?

• [ ] 1 Basic functionality
  • [ ] 1.1 Loading and building correct tree structure when group hierarchy is expanded
  • [ ] 1.2 Loading and building correct tree structure when group hierarchy is not expanded
  • [ ] 1.3 Loading new groups/concepts into group hierarchy
  • [ ] 1.4 Displaying group hierarchy in UI
• [ ] 2 Partial page load
• [ ] 3 CSS & layout
  • [ ] 3.1 Correct sidebar sizing
  • [ ] 3.1.1 Correct height and width on load
  • [ ] 3.1.2 Correct width on window resize
  • [ ] 3.2 Icons and lines
  • [ ] 3.3 Highlighting selected group/concept
  • [ ] 3.4 Colors, text weight, etc.
  • [ ] 3.5 Loading spinners
• [ ] 4 Configuration options
  • [ ] 4.1 showNotation (showing notation codes in group hierarchy)
• [ ] 5 Sorting groups/concepts by label according to localization
• [ ] 6 Cypress tests
• [ ] 7 Showing concept members if the group has other groups as members (see #620)