Document a working solution to disable ECCX08

Author: pennam

README.adoc

@@ -10,8 +10,27 @@ image:https://github.com/{repository-owner}/{repository-name}/actions/workflows/
 Port of https://bearssl.org[BearSSL] to Arduino.
 
 This library depends on ArduinoECCX08. This dependency could be
-disabled by defining ARDUINO_DISABLE_ECCX08 in ArduinoBearSSLConfig.h
-(see examples).
+disabled by defining ARDUINO_DISABLE_ECCX08 in ArduinoBearSSLConfig.h.
+
+To do this create a configuration library called ArduinoBearSSLConfig with the
+following file structure:
+
+```
+└── ArduinoBearSSLConfig/
+    ├── src/
+    │   └── ArduinoBearSSLConfig.h
+    └── library.properties
+```
+
+ArduinoBearSSLConfig.h
+```
+#pragma once
+#define ARDUINO_DISABLE_ECCX08
+```
+library.properties
+```
+name=ArduinoBearSSLConfig
+```
 
 == License ==