Add a way to quote array shape keys. Quote characters that aren't whitelisted for array keys.

[TysonAndre]

E.g. render the array shape type (in issue messages) of [' ' => 'x'] as array{"\x20":string}

TODO: decide on a whitelist.

[TysonAndre]

Or array{\x20:string} since backslashes aren't allowed, plus other escapes (\u..., \\, \n, etc)