MathJax kata preview fixes

[billti]

This fixes an issue with \braket where it was doubling up the entries. The preview today shows:

The fix was to replace physics with braket package. (Not sure why, will log a MathJax bug for that also).

The below two items I was playing with a week ago, but including here:

• Made the page render one kata at a time, and supports linking to a kata via the URL and forward/back navigation between katas without a page reload. (As on slow machines putting every kata on the one page was too slow)
• Converted to Preact to match the rest of our code, instead of manipulating DOM elements directly.

[github-actions]

Benchmark for 40320d1

Click to view benchmark

Test	Base	PR	%
Array append evaluation	344.6±1.87µs	342.2±2.37µs	-0.70%
Array literal evaluation	199.3±8.67µs	179.7±2.55µs	-9.83%
Array update evaluation	428.8±14.88µs	423.9±4.82µs	-1.14%
Core + Standard library compilation	17.5±0.21ms	19.1±0.79ms	+9.14%
Deutsch-Jozsa evaluation	5.1±0.18ms	5.1±0.10ms	0.00%
Large file parity evaluation	33.7±0.09ms	33.7±0.61ms	0.00%
Large input file compilation	11.9±0.26ms	13.0±0.55ms	+9.24%
Large input file compilation (interpreter)	46.2±1.52ms	49.1±1.28ms	+6.28%
Large nested iteration	35.3±1.46ms	33.3±0.52ms	-5.67%
Perform Runtime Capabilities Analysis (RCA) on Deutsch-Jozsa sample	1550.9±34.71µs	1557.7±78.21µs	+0.44%
Perform Runtime Capabilities Analysis (RCA) on large file sample	7.8±0.12ms	8.0±0.07ms	+2.56%
Perform Runtime Capabilities Analysis (RCA) on teleport sample	1423.8±81.01µs	1411.5±35.13µs	-0.86%
Perform Runtime Capabilities Analysis (RCA) on the core and std libraries	27.3±0.49ms	27.6±0.23ms	+1.10%
Teleport evaluation	86.8±3.73µs	86.6±4.42µs	-0.23%

[Manvi-Agrawal]

Made the page render one kata at a time, and supports linking to a kata via the URL and forward/back navigation between katas without a page reload.

Thanks @billti for doing this to improve dev productivity. I was really wishing this feature last week when working on migration of "Superdense Coding" kata because it was slightly annoying to go down and select the kata each time with local changes :)

[tcNickolas]

Looks great! Now I can use this preview on my slow machine :-)