CascadiaCode: Rehint and use ttf

[why]
A lot people (read: People on Windows) have the variable font (VF) version of
Cascadia Code installed - it comes bundled with Windows Terminal.

The static Cascadia Code instances that we use for patching are hinted
with ttfautohint which creates small sized glyphs that are visibly very
different. People compare the static Caskaydia Cove with the VF Cascadia
Code and are surprised.

[how]
First switch from the CFF outlines to TTF outlines - that is the
original version (i.e. otf -> ttf). It is unknown why we created patched
CFF fonts instead of the TTFs. To get as close as possible to the
intended look of the glyphs we should stick with the outline type.

Then we need to re-hint all the fonts, to get hints that are comparable
to the VF hints. We can not use the hints of the VF because the outlines
are different: The VF has (of course) overlapping outlines, while the
static ones (as usual) have not.

The re-hinting can be done with VTT or TTH - both showed results that
are more like the original VF font. The usual ttfautohint has been used
of the static fonts in the font release and can not be used. It is the
reason for this whole problem.

* Used VTT 6.35
* Open font file in VTT
* Import all programs
* Generate 'VTT talk' via Tools -> AutoHint -> LightLatinAutoHint
* Save font file as ...

References:
microsoft/cascadia-code#371
https://learn.microsoft.com/en-us/typography/tools/vtt/

Closes: #998

Signed-off-by: Fini Jastrow <ulf.fini.jastrow@desy.de>

src/unpatched-fonts/CascadiaCode/README.md

@@ -4,4 +4,17 @@
 
 For more information have a look at the upstream website: https://github.com/microsoft/cascadia-code
 
+## Preprocessed Source Font
+
+This source font has been preprocessed - it is not taken directly from upstream.
+Cascadia Code is mainly a variable font (VF) and the static versions (that Nerd Fonts
+are based on) are prepared in a different way: They have been hinted with `ttfautohint`.
+That hints differ considerably from the hints in the VF. That changes the rendering for
+smaller sizes (usual sizes in terminals) considerably.
+
+To get the 'original' (i.e. VF) feel of the font we redo the hints in the static versions:
+Open the font with Microsoft's VisualTrueType (VTT) and apply Light Latin Autohint.
+The issue is known upstream and will probably be fixed. But until it is fixed we need
+to do this manual process on all source updates.
+
 Version: 2111.01