escape dollarsign in tab completion (#13988)

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fixes #13518 

This pr escapes file/directory names, which start with a dollar sign
since it's being interpreted as a variable.

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crates/nu-cli/src/completions/completion_common.rs

@@ -267,8 +267,10 @@ pub fn escape_path(path: String, dir: bool) -> String {
     let filename_contaminated = !dir && path.contains(['\'', '"', ' ', '#', '(', ')']);
     let dirname_contaminated = dir && path.contains(['\'', '"', ' ', '#']);
     let maybe_flag = path.starts_with('-');
+    let maybe_variable = path.starts_with('$');
     let maybe_number = path.parse::<f64>().is_ok();
-    if filename_contaminated || dirname_contaminated || maybe_flag || maybe_number {
+    if filename_contaminated || dirname_contaminated || maybe_flag || maybe_variable || maybe_number
+    {
         format!("`{path}`")
     } else {
         path