Add an installation script

Script will download the latest binary from master and create a systemd
unit file to start it.

install.sh

@@ -0,0 +1,35 @@
+#!/bin/bash
+
+INSTALLDIR=/opt/tempgopher
+INSTALLBIN=$INSTALLDIR/tempgopher
+INSTALLUSER=pi
+BINURL='https://gitlab.com/shouptech/tempgopher/-/jobs/artifacts/master/raw/tempgopher?job=build'
+CONFIGFILE=$INSTALLDIR/config.yml
+
+# Download binary
+sudo mkdir -p $INSTALLDIR
+sudo curl -L $BINURL -o $INSTALLBIN
+sudo chmod +x $INSTALLBIN
+sudo chown -R $INSTALLUSER: $INSTALLDIR
+
+# Create unit file
+sudo sh -c "cat > /etc/systemd/system/tempgopher.service" << EOM
+[Unit]
+Description=Temp Gopher
+After=network.target
+
+[Service]
+Type=simple
+WorkingDirectory=$INSTALLDIR
+ExecStart=$INSTALLBIN -c $CONFIGFILE run
+ExecReload=/bin/kill -HUP \$MAINPID
+User=$INSTALLUSER
+Group=$INSTALLUSER
+
+[Install]
+WantedBy=multi-user.target
+EOM
+
+sudo systemctl daemon-reload
+sudo systemctl enable tempgopher.service
+sudo systemctl start tempgopher.service