feat: add mail section in local dev

docs/ecolyo/Technical/mail.md

@@ -75,6 +75,17 @@ const mjml2html = require('mjml-browser');
 
 - [Mjml live editor](https://mjml.io/try-it-live/bohYnxKkCq-)
 
+### Send mails in local development
+
+Build the app in dev mode and run the desired service.
+
+```sh
+yarn build-dev
+yarn run cozy-konnector-dev -m manifest.webapp ./build/services/monthlyReportNotification/ecolyo.js
+```
+
+Mailhog will intercept the mails and display them at http://cozy.tools:8025/
+
 ## Bounce token
 
 A bounce token stored in the profile of each user is sent in email. It allows us to track if user clicks on links.