switch the default font to TeX Gyre Heros

[exaexa]

(freer than helvetica from mscorefonts, has more unicode support, and a distribution-friendly license)

Kinda related to #67 .

Closes #66 .

[davibarreira]

Makie ships helvitca, is their version different in any way? In order to change from helvetica to tex gyre, we should add it to the assets.

[exaexa]

Maybe Makie will have license issues too. If this seems acceptable I'll add some of the fonts.

[exaexa]

oh whoops, fixed a typo. 😅

[exaexa]

ok I looked at the tests and since the other font is very slightly different, it fails the exact tests now.

I guess I should simplify more.

[exaexa]

@davibarreira hey btw while I'm at this -- since I'll have to change all numbers in the tests ( :D ), wouldn't it be useful to incorporate one other improvement I was wondering? In particular, Vizagrams may ask FreeType directly for the metrics of a whole string instead of pasting together individual glyphs. As the main benefit, that eliminates almost all metric errors (in this case mostly from kerning). With SVG output we can also (mostly) ignore issues like hinting, and thus the change should be able to get perfect text envelopes right away.

[davibarreira]

This sounds good! The way the package handles text is not ideal, as I did it mostly with the goal of getting it working for my thesis. When it comes to LaTeX, it is even worst. haha
If you manage a better solution, I'd be glad to incorporate it.

[exaexa]

Haha yeah to simulate what LaTeX does you need to simulate Knuth, not really an option :D But the kerning (and ligatures, using the same trick) is not complex to handle and covers 99.999999% of cases where font rendering gets completely off.