* Improve \sqrt
Make \sqrt out of inline SVGs to ensure a perfect match at the junction between surd and viniculum.
* Tweak for kern clarity
* Fix lint error
* regenerate screenshot tests with sqrts
* Correct advance
Edit the SVG paths so that they have the correct left bearing and advance width values.
This will correct the spacing on the left side of each surd and it will also improve the placment of a root indice.
* Revise scriptstyle surds
In the `main` size, delimiters *do* scale with scriptstyle and scriptscriptstyle.
* update screenshot images containing sqrts
* Improve rule coding.
* Rule widths (overline, underline, fraction, sqrt) actually scale
with the current font size in AMS-TeX. Implement that. (Sqrt is
a special case: the rule width depends on the font size *of the
surd*.)
* Change the CSS coding for rules. The old, complex coding prevented
variable-width lines and may have contributed to issues like #696.
Its purpose, according to 0a3a2271f4,
was IE8 support; but KaTeX no longer supports IE8.
* The 0.5px offset makes larger sizes better, smaller sizes worse.
Smaller sizes seem more important.
* Cleanup (intended to be squashed).
