fix: unmatched parens backtracking + keep indent

[litoj]

This PR provides better parsing, trying to backtrack to a state when all parenthesis were correctly matched if the first pass had been invalid. This helps in situations when there are calculations made outside a method or markdown numbered list:

4) 4+4 - now correctly parsed
4. 4+4 - already works
method(arg1, 4) 4+4 - now works, useful when calculating for myself on the same line

Also the expression is now being evaluated from the first non-space character, keeping original indent in tact.

[litoj]

Is there something that could be improved upon to get this PR merged?

[litoj]

Hi, I just wanted to give a heads up that I consider this PR finished, so I wanted to ask @hrsh7th if you would consider merging it.

[litoj]

@hrsh7th ping

[hrsh7th]

thank you!