patch 8.2.2212: Vim9: lambda with => does not work at the script level

Problem:    Vim9: lambda with => does not work at the script level.
Solution:   Make it work.
diff --git a/src/eval.c b/src/eval.c
index e3a3592..df5b842 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -3349,8 +3349,13 @@
 
     /*
      * nested expression: (expression).
+     * lambda: (arg) => expr
      */
-    case '(':	{
+    case '(':	ret = NOTDONE;
+		if (in_vim9script())
+		    ret = get_lambda_tv(arg, rettv, TRUE, evalarg);
+		if (ret == NOTDONE)
+		{
 		    *arg = skipwhite_and_linebreak(*arg + 1, evalarg);
 		    ret = eval1(arg, rettv, evalarg);	// recursive!