Initial assessment: symlink command already implemented, needs tests and documentation

Co-authored-by: imjasonh <210737+imjasonh@users.noreply.github.com>

test_symlink.rs

@@ -0,0 +1,9 @@
+use testscript_rs::testscript;
+
+#[test]
+fn test_symlink() {
+    testscript::run("/tmp")
+        .filter_file("test_symlink.txtar")
+        .execute()
+        .unwrap();
+}

testdata/test_symlink.txt

@@ -0,0 +1,8 @@
+# Test symlink functionality
+symlink original.txt link.txt
+exists link.txt
+exec cat link.txt
+stdout "original content"
+
+-- original.txt --
+original content