KaTeX update

[arunpersaud]

Pull Request Checklist

• I’ve read the guidelines for contributing.
• I updated AUTHORS.txt and CHANGES.txt (if the change is non-trivial) and documentation (if applicable).
• I tested my changes.

Description

tested by creating a demo site and adding

$$\\sin(x) = \\frac{1}{3}$$                                                                          
\\begin{align*} \\sin(x) &= \\frac{1}{3} \\\\  \\cos(x)+5  &= \\int^1_0\exp(x) \\end{align*}         

to the post.

Based on #3710, Fixes #3709

Review needed since I haven't used math mode in nikola before and, for example, not sure about "double " needed in input. Also, KaTeX seems to support some more environment and I'm not sure if the the setup one should only use the * version of those or the one without star or both?

[Kwpolska]

Suggested change

	# {left: "\\\\[", right: "\\\\]", display: true}
	# {left: "\\\\[", right: "\\\\]", display: true},

[Kwpolska]

Double backslashes are usually required when using markdown or reST, we can’t do much about it.

The default value that KaTeX uses is:

[
  {left: "$$", right: "$$", display: true},
  {left: "\\(", right: "\\)", display: false},
  {left: "\\begin{equation}", right: "\\end{equation}", display: true},
  {left: "\\begin{align}", right: "\\end{align}", display: true},
  {left: "\\begin{alignat}", right: "\\end{alignat}", display: true},
  {left: "\\begin{gather}", right: "\\end{gather}", display: true},
  {left: "\\begin{CD}", right: "\\end{CD}", display: true},
  {left: "\\[", right: "\\]", display: true}
]

We should probably use that and add equation*, because IIRC some input format will generate that. I’m not sure about align vs align*, we probably want both.

[arunpersaud]

Added equation and align* and fixed the missing comma.

[arunpersaud]

just checking in, if anything else is needed here