add flameshot client example

contrib/flameshot.sh

@@ -0,0 +1,14 @@
+#!/bin/bash
+set -e
+
+# take a screenshot with flameshot and send it to copyparty;
+# the image url will be placed on your clipboard
+
+password=wark
+url=https://a.ocv.me/up/
+filename=$(date +%Y-%m%d-%H%M%S).png
+
+flameshot gui -s -r |
+curl -T- $url$filename?pw=$password |
+tail -n 1 |
+xsel -ib