Update packages and linting

[zorkow]

• Updates all packages to latest version except for typescript
• Fixes all linting errors of the form no-useless-assignment. These generally make things clearer. The only exceptions are in Wrappers/mo.ts and Wrappers/mmultiscripts.ts where it makes things slightly uglier.

[dpvc]

One issue with an incorrect comment, but otherwise ok.

[dpvc]

I think this is removing spaces, not {. After #1539, it will also remove comments.

[zorkow]

GetNext removes spaces and gets the next non-whitespace characters. But then we ignore that and then c to the next character. So does that not mean that we are effectively ignore the initial characters, which in the tests was always { ?

[dpvc]

No, GetNext() does return the next character, but doesn't move past it. And the next character isn't a { in the case where you have a template, like \def\x#1{...} or \def\x#1,#2\end{...}.

MathJax-src/ts/input/tex/TexParser.ts

Lines 298 to 303 in fb98717

	public GetNext(): string {
	while (this.nextIsSpace()) {
	this.i++;
	}
	return this.getCodePoint();
	}