media files not suitable for prefix with _ underscore

[shanehh]

https://github.com/finalion/WordQuery/blob/99f6377e26fdce4abeed29fe53bfa2896b17232e/src/service/youdao.py#L149

ref: https://apps.ankiweb.net/docs/manual20.html

Rename the file, adding an underscore at the start, so it becomes like "_arial.ttf". Adding an underscore will tell Anki that this file will be used on a template, and should not be deleted when checking for unused media.