modules/tex/template.tex: allow the unicode prime symbol instead of \prime

[ioistired]

I don't really know how to do this, but is it possible to allow "′" (U+2032 PRIME), " ″" (U+2033 DOUBLE PRIME), "‴" (U+2034 TRIPLE PRIME), and "⁗" (U+2057 QUADRUPLE PRIME) to be used?
For example, (f^{-1})^′ instead of (f^{-1})^{\prime}

The first one would be defined as \prime but I don't know what the rest should be defined as.

[DXsmiley]

The rest would just be defined as {\prime \prime \prime}, I think.

[DXsmiley]

I could map them to either {\prime} or ^{\prime}. I think the second one would be better, since it requires less typing, and seems to fir the general usecase for ′ a bit better. Screenshot of what happens with each is below.

[ioistired]

ew light theme yeah LGTM