Proper kerning of \XeTeX

[pkgw]

Right now we don't properly kern the backwards E in \XeTeX, purely just because I needed to customize the macro and didn't take the time to replicate it.

To fix this, we need to make our overridden macro a bit more sophisticated, here:

https://github.com/tectonic-typesetting/tt-weave/blob/main/template/src/xetex-overrides.tex#L6

A macro with proper kerning would need to be wrapped in the \special commands to turn the full expression into a "canvas", as in the version of the \TeX macro redefined in the preamble:

https://github.com/tectonic-typesetting/tt-weave/blob/main/template/src/_preamble.tex#L59-L60

Note that the \XeTeX currently uses the wrapped \TeX expression in its definition. I'm not sure what will happen if we try to nest canvases by keeping things that way!