new: [plausible] add charm

plausible/hooks/web_proxy-relation-joined

@@ -0,0 +1,16 @@
+#!/bin/bash
+
+set -e
+
+DOMAIN=$(relation-get domain) || {
+    echo "Failed to get domain"
+    exit 1
+}
+
+config-add "\
+services:
+  $MASTER_BASE_SERVICE_NAME:
+    environment:
+      BASE_URL: \"https:\/\/${DOMAIN}\"
+"
+