Consider switching back to upstream kjua version

[rugk]

Background

In #188 we switched to to https://github.com/werthdavid/kjua/, a fork of the kjua lib that initially mostly just added SVG support (see lrsjng/kjua#7)

Now, however, the upstream author also added SVG support in a smaller way without an extra lib.

Proposed solution

Switch back to https://github.com/lrsjng/kjua

Alternatives

Keep the fork by @werthdavid given it works. (and maybe has other advantages?)
AFAIK we, however, do not make use of other differences, e.g. a transparent background e.g. is usually always given if we use an SVG. (respectively we always need to specify a color 😉)

Additional context

This could also improve/fix #248, because of a smaller code base without so much eval etc.