add check version each arch

[malikshi]

i tested on arm64, i don't have mips devices at my current locations fix: https://github.com/adyanth/openwrt-tailscale-enabler/issues/37

[BJReplay]

I tested this on arm (not arm64).

I didn't replace the if with case but did test the fetching of the latest version and it upgraded my EA8500 from 1.46.0 to 1.48.0 successfully.

In effect, I took the snippet below only:

    latest_version=`wget -O- https://pkgs.tailscale.com/stable/ | grep -o "tailscale_[0-9.]*_${arch}.tgz" | grep -o '[0-9.]*' | head -n 1`

    if [ -z "$latest_version" ]; then
        echo "Error: Failed to fetch the latest Tailscale version for $arch architecture."
        exit 1
    fi

    tailscale_version="1.46.0"  # Your desired version (fallback if fetching the latest fails)

    if [ "$tailscale_version" != "$latest_version" ]; then
        tailscale_version=$latest_version
    fi