minor: integrate invoices

README.md

@@ -424,6 +424,36 @@ Where:
 
 Setting custom langs will not allow user to choose their own lang.
 
+### Invoices
+
+Invoices allow your Projects to manage invoices
+
+Project is mandatory.
+
+You'll need:
+
+On Server: `djangoldp_invoice` packages
+
+Module declaration, on `config.json`:
+
+```json
+    {
+      "type": "projects",
+      "extensions": [
+        {
+          "type": "invoices",
+          "endpoints": {
+            "uploads": "http://server.url/upload/"
+          }
+        }
+      ]
+    }
+```
+
+Where:
+
+* `xmpp` is your [Prosody](https://prosody.im/) with [appropriate modules](https://git.startinblox.com/infra/prosody-modules/) configured on.
+
 ### Job Offers
 
 Job Offers includes a job board with conversation. To activate them