Add Matrix/Riot package and updated README

package-riot/templates/riot-nginx.j2

@@ -0,0 +1,16 @@
+# Simple and straightforward web server for Riot
+# {{ ansible_managed }}
+server {
+	listen 80 default_server;
+	listen [::]:80 default_server;
+
+	root /var/www/riot;
+
+	index index.html;
+
+	server_name _;
+
+	location / {
+		try_files $uri $uri/ =404;
+	}
+}