cascadia-ttf: update to 2106.17.

Features:

- Arabic (and Urdu) support added (design by Mohamad Dakak) (#84)
    - See the Arabic features PDF for the exciting new Arabic ligature
      functionality used in Cascadia Code that gives the font greatly improved
      readability and feel more more akin to a text typeface.
    - Don't want all that? Don't worry, Cascadia Mono will house a normal
      version of Arabic.

- Hebrew support added (design by Liron Lavi Turkenich) (#465)

- Due to popular demand, we've introduced a more "toned-down" version of
  Cascadia Italic, which does away with a number of the cursive letter forms.
  (#468)
    - Entry and exit strokes across the italic lowercase have been rounded
      to better achieve the fun / playful design language that we intended
      for the italic. Other skeletons have been modified as necessary.
      Cyrillic has also been updated for better consistency with the new
      design.
    - You can now activate the original cursive versions of /f /l /s and
      /r with typographic feature salt or ss01.

Changes:

- We have adjusted the slant on all of the italic letters to make sure it's
  consistent (#470)
- Italic Only: #507 - bar and broken bar will now stay upright for better
  clarity
- Fixing a bug in the ccmp feature file and added ccmp to the feature
  set in the build script.
- Deleting the (unused) liga feature file
- Vika has reviewed and improved some forms in Cascadia Code upright.
- Greek lowercase has been updated per feedback from Gerry Leonidas to
  be more cohesive (No longer a mix between a "Monday" and "Friday" font.
  All Friday, all the time!)
- #422 - Bitcoin glyph added
- #427 - FFFD glyph added
- #418 - top bar corrected
- #433 - hinting corrected to ensure alignment
- #435 - adds consistent ligature form for =>> <<= =<< and
  >>= (the infinite arrows still work with addition of more equals)
- #443 - ligature now ignores (*) scenario
- #454 - adds ignore to prevent equal_equal ligature from showing up
- #467 - Not specifically sure of the problem here, but suspect that it will
  be fixed with this - update.
- #477, #478, #479, #480 - interpolation issues fixes in a lot of ligatures
- #481 - JetBrains enumerates fonts weird. We've modified the internal naming
  so that it will register Cascadia Code correctly. Also aligned postscript
  naming with Google's recommendation, so will show up as "Regular" instead of
  "Roman".
- General improvement of weight balancing
- Weight of lowercase rounds reduced in the Bold weight in Cascadia Code.
- Weight of Capital stems increased in Extralight weight in Cascadia Code.
- Tweaked weight of ogonek in ExtraLight.
- Added a localized form for 蝶 and 腸 should a user chose to use those
  codepoints and want an accented version.
- Split fraction bar at heavier weights to improve clarity of fractions.
- Adjusted standard box drawing characters to align with GDI metrics, and added
  a complete set of DWrite-specific ones that align with sTypo (using rclt).
- Ironed out some tiny inconsistencies in the <$ $> <$> ligatures which
  we suspect no one will ever notice.
- Fixed centering of braces and some hyphens.
- Fixed inconsistency between semicolon/colon and period weight in bold. Also
  fixed slight differences in hyphen-like glyphs in bold. You're as surprised
  as we are.
- Increased weight of underscore in bold.
- Changed design of commaaccent, commaaccentmod commaturnedabove and commaabove
  to be more distinguishable (following design of quotes).
- Fixed descents of various greek lowercase glyphs that were inconsistent.
- Felt ligated, might edit later.
- Corrected some additional interpolation bugs


(fcambus)