Add parser (and etc.) support for print statements.

src/syntax/tokens.rs

@@ -11,6 +11,9 @@ pub enum Token {
     #[token(";")]
     Semi,
 
+    #[token("print")]
+    Print,
+
     #[regex(r"[+\-*/]", |v| v.slice().chars().next())]
     Operator(char),
 
@@ -35,6 +38,7 @@ impl fmt::Display for Token {
         match self {
             Token::Equals => write!(f, "'='"),
             Token::Semi => write!(f, "';'"),
+            Token::Print => write!(f, "'print'"),
             Token::Operator(c) => write!(f, "'{}'", c),
             Token::Number((None, v)) => write!(f, "'{}'", v),
             Token::Number((Some(2), v)) => write!(f, "'0b{:b}'", v),