btop reads the `LANG` env variable to delect if the system has utf8
support, which exists on common Linux distributions.
However, OpenWrt does not ship it, and results in btop reporting
"No UTF-8 locale detected!". Users have to manually pass `--utf-force`
to make btop happy.
To make it OOTB, append `--utf-force` argument by default via alias.
Signed-off-by: Tianling Shen <cnsztl@immortalwrt.org>
