chore: str as_bytes() doc

docs/language_concepts/00_data_types.md

@@ -152,6 +152,20 @@ fn main(message : pub str<11>, hex_as_string : str<4>) {
 }
 ```
 
+You can convert a `str<N>` to a byte array by calling `as_bytes()`
+or a vector by calling `as_bytes_vec()`.
+
+```rust
+fn main() {
+    let message = "hello world";
+    let message_bytes = message.as_bytes();
+    let mut message_vec = message.as_bytes_vec();
+    assert(message_bytes.len() == 11);
+    assert(message_bytes[0] == 104);
+    assert(message_bytes[0] == message_vec.get(0));
+}
+```
+
 ## Compound Types
 
 A compound type groups together multiple values into one type. Elements within a compound type can