* 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
* Use inline SVG for stretchy elements
Replace all background-images with inline SVG code.
Pros:
* `\color` works in all browsers, even IE/Edge
* Better printing
* Much simpler CSS
* No links to background-images
* No `mask`
* No browser-detection
* No external SVG files
* Faster first rendering
Cons
* No image caching
* Heavier HTML load
* Larger JavaScript file
* `\cancel` line is in `px` units, not `em` units
* Remove static/images from make file
* Change \cancel from px to em
* regenerate screenshots for functions using inline svg
Summary:
Stuff like `\red{\overbrace{AB}}` works now in addition to `\color{red}{\overbrace{AB}}`. Strikethrough now respects color. The Firefox in the screenshotter doesn't seem to support `background-image` + `mask`, but I manually tested that the latest Firefox does.
Test plan:
Ran `make`, then tested in latest Chrome and Firefox to ensure color support was working, then ran `make screenshots`.
