This PR:
- brings back [this PR](https://github.com/YunoHost/yunohost-config-nginx/pull/3/files) which seems to have stayed behind when migrating from `yunohost-config-nginx`. It fixes the missing tile for Jirafeau app (and maybe others).
- adds a fix to serve `ynhpanel.*` files whatever the app ningx rules are (some apps nginx conf files block them, like duniter or nextcloud).