feat: press tab inserts language specific num of spaces or default

[divSelector]

This is addressing the issue posted here

#195

I noticed that there was already this object that wasn't being used

let indents = {
    "default": " ".repeat(4),
    "python": " ".repeat(4),
    "python2": " ".repeat(4),
    "html": " ".repeat(2),
    "css": " ".repeat(2),
    "javascript": " ".repeat(2),
};

So I assumed that someone intended to eventually use it and I just decided to plug it in.

The number of indents is determined like this let indent = indents[lexer.toLowerCase()] || indents["default"];

The logic that checks for Python is taken out since it's already handled above.

I thought about writing a function const f = n => " ".repeat(n) so that the indents object could just contain integers, but I didn't really want to make design decisions for you.

The numbers that are put into the languages are obviously opinionated. You could change the defaults to whatever you preferred.

[supakeen]

Looks good to me, we'll see if anyone gets confused by this :)