Fix README 'aiken new' example.

crates/aiken/src/cmd/new.rs

@@ -115,9 +115,9 @@ fn readme(root: &Path, project_name: &str) -> miette::Result<()> {
 
                 For example, as `validators/always_true.ak`
 
-                ```gleam
-                validator {{
-                  fn spend(_datum: Data, _redeemer: Data, _context: Data) -> Bool {{
+                ```aiken
+                validator my_first_validator {{
+                  spend(_datum: Option<Data>, _redeemer: Data, _output_reference: Data, _context: Data) {{
                     True
                   }}
                 }}
@@ -133,7 +133,7 @@ fn readme(root: &Path, project_name: &str) -> miette::Result<()> {
 
                 You can write tests in any module using the `test` keyword. For example:
 
-                ```gleam
+                ```aiken
                 test foo() {{
                   1 + 1 == 2
                 }}