Use b-string instead of array of b-chars

ablescript/src/variables.rs

@@ -208,7 +208,7 @@ impl Value {
             Value::Str(s) => Functio::Eval(s),
             Value::Int(i) => Functio::BfFunctio {
                 instructions: {
-                    let instruction_mappings = [b'[', b']', b'+', b'-', b',', b'.', b'<', b'>'];
+                    let instruction_mappings = b"[]+-,.<>";
                     std::iter::successors(Some(i as usize), |i| {
                         Some(i / instruction_mappings.len())
                     })