CodeMirror: WebAssembly mode

## WebAssembly mode

/* Example WebAssembly */ (module $foo (export "fac" (func $fac)) (export "plus" (func $plus)) (func $fac (type $t0) (param $p0 i64) (result i64) (if $I0 (result i64) (i64.lt_s (local.get $p0) (i64.const 1)) (then (i64.const 1)) (else (i64.mul (local.get $p0) (call $fac (i64.sub (local.get $p0) (i64.const 1))))))) (func $plus (param $x i32) (param $y i32) (result i32) (i32.add (local.get $x) (local.get $y))))

MIME types defined: `text/webassembly`.