dnscrypt-proxy-switcher doesn't work if user has manually changed interface name

In recent MacOS, the user is able to manually change the name of the network interface in the "Network" pane of the System Settings. If the user does this, then the **dnscrypt-proxy-switcher** script fails for that interface as the script is trying to use the hardware interface name, not the network interface name and then the '`networksetup -setdnsservers`' call fails.

Fortunately, there is a simple fix. Line 63 of the script needs to be changed.
Old line 63: `currentservice="$sname"`
New line 63: `currentservice=$(networksetup -listnetworkserviceorder | grep -B1 "Device: $sdev" | head -n1 | sed 's/^([0-9]*) //')`

This new line takes the active network interface (e.g., 'en3') and then uses the `networksetup` tool to find the interface name associated with that network interface.

In addition line 58 (`sname=$(echo "$line" | awk -F "(, )|(: )|[)]" '{print $2}')`) can now be commented out as it is unnecessary.

Open the dnscrypt-proxy-switcher script and inspect lines 58 and 63. Verify the network service lookup with networksetup; done means manually renamed macOS interfaces no longer cause the networksetup -setdnsservers call to fail.

Written by the indexing model from the issue text.