Add stack pointer with 1MiB

[RoyalIcing]

Zig: ziglang/zig#5529
Rust: rust-lang/rust#50083

Both do stack-size=1048576

Zig produces a wasm file with:

(memory (;0;) 17)
(global (;0;) (mut i32) (i32.const 1048576))

[RoyalIcing]

I’ve decided this is a good lesson, but perhaps one a higher-level library like SilverOrb can use.