feat(renderer): add NO_COLOR and TERM support to Config

[johnyob]

Grace's renderer will now infer NO_COLOR and TERM for Config.default.

Behaviour

No color

$ NO_COLOR=1 dune exec main
error: `match` cases have incompatible types # <-- this is bold
    ┌─ fizz.ml:7:13
  2 │    let fizz n = 
  3 │ ╭──  match n mod 5, n mod 3 with
  4 │ │    | 0, 0 -> `Fizz_buzz
    │ │              ---------- this is found to be of type `[> `Fizz_buzz]`
  5 │ │    | 0, _ -> `Fizz
    │ │              ----- this is found to be of type `[> `Fizz]`
  6 │ │    | _, 0 -> `Buzz
    │ │              ----- this is found to be of type `[> `Buzz]`
  7 │ │    | _, _ -> n
    │ │              ^ expected `[> `Buzz | `Fizz | `Fizz_buzz]`, found `int`
    │ ╰──────────────' `match` cases have incompatible types
  8 │    ;;

No highlighting or color

$ TERM=dumb dune exec main
error: `match` cases have incompatible types
    ┌─ fizz.ml:7:13
  2 │    let fizz n = 
  3 │ ╭──  match n mod 5, n mod 3 with
  4 │ │    | 0, 0 -> `Fizz_buzz
    │ │              ---------- this is found to be of type `[> `Fizz_buzz]`
  5 │ │    | 0, _ -> `Fizz
    │ │              ----- this is found to be of type `[> `Fizz]`
  6 │ │    | _, 0 -> `Buzz
    │ │              ----- this is found to be of type `[> `Buzz]`
  7 │ │    | _, _ -> n
    │ │              ^ expected `[> `Buzz | `Fizz | `Fizz_buzz]`, found `int`
    │ ╰──────────────' `match` cases have incompatible types
  8 │    ;;