Components that need styling

[flachware]

• [x] Rework annotation design based on draft annotation-4 #30.
• [x] Update annotation styles to clamped-view. #34
• [x] Soften highlight color in PDF #32
• [x] Add color split button to page-popup #35
• [x] Search #38
• [x] Import bar #39
• [x] Error message #41
• [x] Note toggle icon (right sidebar)
• [ ] Down / focus state
• [ ] Page number editing
• [ ] Editor bubble
• [ ] Cursors in PDF viewer
• [ ] Loading bar
• [x] Blurred window state
• [ ] keyboard focus states in generic theme
• [ ] Update styles due to https://github.com/zotero/zotero-pdf.js/issues/10
• [ ] Hairline styles (toolbar buttons, search box, …) for generic theme on high-res displays