Add starts with operator (#5061)

* add starts_with operator

* added a test

src/tests/test_parser.rs

@@ -315,6 +315,14 @@ fn capture_row_condition() -> TestResult {
     )
 }
 
+#[test]
+fn starts_with_operator_succeeds() -> TestResult {
+    run_test(
+        r#"[Moe Larry Curly] | where $it =^ L | str collect"#,
+        "Larry",
+    )
+}
+
 #[test]
 fn proper_missing_param() -> TestResult {
     fail_test(r#"def foo [x y z w] { }; foo a b c"#, "missing w")