websites/proxy-matrix: Add Synapse rev proxy setup

The *websites/proxy-matrix* role configures the Internet-facing reverse
proxy to handle the *hatch.chat* domain.  Most Matrix communication
happens over the default HTTPS port, and as such will be directed
through the reverse proxy.

roles/websites/proxy-matrix/tasks/main.yml

@@ -0,0 +1,6 @@
+- name: ensure apache is configured to proxy for matrix
+  template:
+    src: matrix.httpd.conf.j2
+    dest: /etc/httpd/conf.d/matrix.conf
+    mode: '0644'
+  notify: reload httpd