Add support of eucal and euscript

I would like to see the `eucal` and `euscript` fonts being supported by KaTeX. These fonts are widely used in mathematics literature.

**Link to or name of a (La)TeX package that provides the same feature:**
I found a [documentation](https://mirror-hk.koddos.net/CTAN/fonts/amsfonts/doc/euscript.pdf) of the `eucal` and `euscript` package, but I cannot find them on CTAN.