Add user flag

[el404]

@TribalWarrior

The latest version of the File Browser in Docker Hub by defaults using user 1000:1000 (a non-root user). This causes permission issues when trying to edit Home Assistant files since Home Assistant typically requires root access (user 0:0) for proper file modification.

We need to add support for a --user flag in the File Browser configuration to override the default user.

Solution here - 【Add-on Guide】Volume management & Filebrowser add-on - #66 by el404