Add Num.atan builtin

compiler/module/src/low_level.rs

@@ -43,6 +43,7 @@ pub enum LowLevel {
     NumPowInt,
     NumFloor,
     NumIsFinite,
+    NumAtan,
     Eq,
     NotEq,
     And,

compiler/module/src/symbol.rs

@@ -646,6 +646,7 @@ define_builtins! {
         41 NUM_FLOOR: "floor"
         42 NUM_ADD_WRAP: "addWrap"
         43 NUM_ADD_CHECKED: "addChecked"
+        44 NUM_ATAN: "atan"
     }
     2 BOOL: "Bool" => {
         0 BOOL_BOOL: "Bool" imported // the Bool.Bool type alias