add a very simple example on JWT and move the previous to the 'overview' sub folder

_examples/auth/jwt/overview/README.md

@@ -0,0 +1,29 @@
+# Generate RSA
+
+```sh
+$ openssl genrsa -des3 -out private_rsa.pem 2048
+```
+
+```go
+b, err := ioutil.ReadFile("./private_rsa.pem")
+if err != nil {
+    panic(err)
+}
+key := jwt.MustParseRSAPrivateKey(b, []byte("pass"))
+```
+
+OR
+
+```go
+import "crypto/rand"
+import "crypto/rsa"
+
+key, err := rsa.GenerateKey(rand.Reader, 2048)
+```
+
+# Generate Ed25519
+
+```sh
+$ openssl genpkey -algorithm Ed25519 -out private_ed25519.pem
+$ openssl req -x509 -key private_ed25519.pem -out cert_ed25519.pem -days 365
+```