Font Overview tasks

[justvanrossum]

Followups for #1849, fixing #102.

The task items are not necessarily ordered by priority.

• [font overview] Add selectable and customizable "template" char sets #1937
• [font overview] Use URL fragment to read/write UI settings #1914
• Design/define what categories we'd like the cell view to use, and how customizable that should be
• [font overview] Implement a form of glyph/character grouping #1903
• Something with unicode properties: https://www.npmjs.com/package/unicode-properties
• [font overview] Improve shift-click behavior and implement shift-arrow-key #1898
• [font overview] Arrow key behavior #1897
• Make side bar resizable
• Implement glyph copy/paste/delete + undo
• Add a context menu
• Add UI to make cell size customizable (menu bar menu items, under "View")
• [glyph-cell] distinguish between "loading" and "glyph not present in font"
• [glyph-cell] add tooltip
  • show the full glyph name (long names get truncated in the cell view)
  • show all code points as U+1234 values (in the future: unicode name)
  • show the first code point as a character
• [font overview] Menu bar for font overview #1845
• Implement click-drag select multiple glyphs (maybe)
• [related-glyphs] "Related Glyphs" should use glyph-cell-view #1887
• [font overview] Add Unicode Block as group-by category #1909
• [font overview] improve grouping of unencoded glyphs #1912

More tasks may be added

All issues shall be prefixed with [font overview], or more specific, for example [glyph-cell]