Add a README to the example directory

example/README.md

@@ -0,0 +1,26 @@
+# Examples
+
+Running one of the examples:
+
+```sh
+cargo run --example <name-of-the-example>
+```
+
+The follow examples exist:
+
+- `echo-dialer` will attempt to connect to `/ip4/127.0.0.1/tcp/10333`, negotiate the `/echo/1.0.0`
+  protocol, then send the `"hello world"` message. Compatible with the `echo-server` example.
+- `echo-server` will listen on `/ip4/0.0.0.0/tcp/10333`, negotiate the `/echo/1.0.0` protocol with
+  each incoming connection, then send back any entering message. Compatible with the `echo-dialer`
+  example.
+
+## How the keys were generated
+
+The keys used in the examples were generated like this:
+
+```sh
+openssl genrsa -out private.pem 2048
+openssl rsa -in private.pem -outform DER -pubout -out public.der
+openssl pkcs8 -in private.pem -topk8 -nocrypt -out private.pk8
+rm private.pem      # optional
+```