[RFC] Add a printf function to the ecma-sl language

[filipeom]

C-Style printf

printf "Hello, %s\n" "World"

Pros:

• Probably can reuse OCaml's format strings to compile our formatter

Cons:

• Harder to typecheck and unpack arguments

Rust-Style format printer

print("Hello, {}\n", "World")

Pros:

• Easier to unpack arguments, no need to typecheck

Cons:

• Harder to compile our format string