Function getFileNameExtension

getFileNameExtension(path: string): string
Extracts the file extension from a file path.
Parameters
- path: string
  The file path from which to extract the file extension.
Returns string
The file extension in lowercase. Returns an empty string if the path is invalid or has no extension.
Example
```
getFileNameExtension("example.txt");       // Returns "txt"
getFileNameExtension("/path/to/file.jpg"); // Returns "jpg"
getFileNameExtension("no_extension");      // Returns ""
getFileNameExtension("");                  // Returns ""
```