* Fix \sqrt zoom in Safari
This PR evades a Safari bug which causes nested SVGs to zoom improperly. `\sqrt` and single-ended arrow SVGs have been modified.
These have been converted from nested SVGs to single level. Their long tails are now sliced off using CSS `overflow: hidden`.
Safari will still improperly zoom any double-ended stretchy arrows and horizontal braces.
* Fix \sqrt{}
Even if the function argument is empty, still render an SVG whose width equals the surd glyph.
* Fix tall \sqrt when scaled
* update screenshots affected by sqrt fixes
* more screenshots after changes to fix sqrt
* Pick up review comments
* Improve SVG Performance
This PR introduces three new classes: `svgNode`, `pathNode`, and `lineNode`. SVG data is then loaded into the domTree exclusively via instances of these classes.
`innerHTML` is banished.
* Fix lint errors
* Fix \cancel typo
* Fix sqrt height
* Adjust min-lenght
Adjust some of the extensible arrows to get a min-length that matches glyph length of the long arrows in KaTeX Main font range from Unicode 27F5 to 27FC.
The accent arrows still get min-lengths that match the arrows in the Unicode 2100 range.
* regenerate screenshots after optimizing SVG code
* update DisplayStyle screenshot for Chrome
* update OverUnderset and Smash screenshots for Chrome as well
* Remove escapes from template strings
* Pick up review comments
* Fix lint errors
* Add comments
* Add \smash, laps, spaces, and phantoms
1. Support `\smash`, including the optional argument from AMS.
2. Change `\llap` and `\rlap` so that they render in text style. Repeat: This *changes* KaTeX behavior.
3. Add `\mathllap` and `\mathrlap`. These will act as they do in `mathtools` and as in previous KaTeX versions of `\llap` and `\rlap`.
4. Add `\mathclap` and `\clap`.
5. Add `\hphantom` and \vphantom`.
6. Add `\thinspace`, `\medspace`, `\thickspace`
7. Add `\hspace`.
This work will resolve issue #270 and parts of #50 and #164.
A. Perlis has written a [concise description](https://www.math.lsu.edu/~aperlis/publications/mathclap/perlis_mathclap_24Jun2003.pdf) of items 1 thru 5. Except for `\smash`'s optional argument. It's described in the [AMS User's Guide](http://texdoc.net/texmf-dist/doc/latex/amsmath/amsldoc.pdf).
Item 6 also comes from the AMS User's Guide.
* Fix test spec
* Exploit makeVList for smash
* update smash and phantom screenshots for chrome
* Pick up review comments
* Change test from \llap to \mathlap
\llap is fundamentally a text-mode function. We should not expect it to work correctly when given math-mode arguments. So test \mathllap instead.
* Correct \llap macro
A correction. The previous macro returned an error if given an argument with math-mode content, such as x^2.
The corrected macro will not return an error. It will instead return well rendered math, but letters are in `\mathrm` font.
* update \llap, \rlap, \clap macros to use \textrm
* update Lap screenshots
