Add traefik config for overleaf service

traefik/config/services/overleaf.yml

@@ -0,0 +1,15 @@
+# /services/traefik/config/services/overleaf.yml
+
+http:
+  routers:
+    tex:
+      entryPoints:
+        - https
+      rule: Host(`tex.eliasfink.de`)
+      service: overleaf
+
+  services:
+    overleaf:
+      loadBalancer:
+        servers:
+          - url: http://overleaf:80