Add proxy configuration to README

Author: endorama

Diff for: README.md

@@ -94,6 +94,23 @@ To create multiple configuration files:
 - restart the agent
 - click the tray bar icon and select the new configuration
 
+## When behind a proxy
+
+The agent support working behind a proxy, but manual configuration is required ( there is no support for automatic proxy discovery ).
+
+To add proxy configuration:
+- stop the agent: tray bar icon -> pause then tray bar icon -> kill
+- find the `config.ini` file that is present in the `arduino-create-agent` installation folder
+- edit the `config.ini` file adding this lines under the `[env]` section ( create it if not present ):
+    ```ini
+    http_proxy=yourproxyhere
+    https_proxy=yourhttpsproxyhere
+    ```
+- restart the agent
+   
+**Tip**: you can also use the multiple configurations feature to create a new configuration with the proxy settings. This way you can have multiple proxies configured and disable proxy configuration with ease.
+
+
 # Contributing
 
 Please use the current latest version: