Allow configuring math.js formatting

[NoahAndrews]

math.js has many options to configure the formatting of its output. Unfortunately, if you're using heynote and you're not happy with the default values, you have to add an explicit format() call everywhere that you want to override them, which is annoying and puts quotation marks around the result that you have to remove when pasting. It would be much better if we could configure the math.js formatting options in the heynote settings.

[heyman]

I've now fixed it (#92) so that string results won't render with quotation marks:

What's the use case for changing the default? I'm hesitant to add settings/features that very few users would use.

[NoahAndrews]

Nice!

The default that got in my way was auto-switching to exponent notation. As a software engineer, I sometimes calculate big numbers that I want be able to paste directly into my code.

[heyman]

I've managed to fix it so that one can override the default format function within a math block, like this:

_format = format
format(x) = _format(x, {notation:"exponential"})
...

It's working, but I'll have to tidy it up and write some tests before I commit it.

Edit:
In my current fix, I've changed it so that if format is defined within the block it'll be used for both the display and copy value. I don't know if it would make sense to have something like formatDisplay and formatCopy instead?

[NoahAndrews]

That was fast, thanks!

[NoahAndrews]

Personally I prefer the behavior of copying exactly what's displayed, so what you have now is fine