Add space between double curly braces to fix issues with cloze cards

[niposch]

Without spaces between double curly braces in Equations inside cloze deletions, this happens in anki:

If we change the math from this:

\frac{\{P\land E\} S \{P\}}{\{P\}\text{while E do S}\{P\land \lnot E\}}

to this:

\frac{\{P\land E\} S \{P\} }{\{P\}\text{while E do S}\{P\land \lnot E\} }

It solves the issue and displays the math properly when reviewing cards.

Resolves #313

[niposch]

Apparently it is possible to do cloze deletions inside math in anki, so this might need a more elaborate approach than just adding a space between every curly.

Anki seems to use this regex for clozes so maybe just matching that and leaving them as is and adding spaces to all other double curlies should resolve this issue:
https://github.com/ankitects/anki/blob/29f9f0dca7799cf270eb41c51a9db0c3ad9fa47d/ts/editable/mathjax.ts#L85

[ShootingKing-AM]

Maybe you can add as an Custom fix, and with a setting which is default off, else it may have unintended side effects.