feat: update readme, add encrypt/decrypt by smart card(yubikey)

README.md

@@ -42,3 +42,26 @@ Encrypt config `~/.tinyencrypt/config-rs.json`:
   }
 }
 ```
+
+Smart Card(Yubikey) protected ECDH Encryption description:
+```text
+┌───────────────────┐                     ┌───────────────────────────┐
+│Tiny Encrypt       │                     │Smart Card (Yubikey)       │
+│                   │  Get Public Key(P)  │                           │
+│                   │ ◄───────────────────┤ Private Key d             │
+│                   │                     │ P = kG                    │
+│                   │ Temp Private Key k  │                           │
+└───────────────────┘ G = kG              └───────────────────────────┘
+
+                      Shared Secret = kP = kdG
+
+                      Store Q, Encrypt using derived key from Shared Secret
+
+
+                      Send Q to Smart Card
+                      ─────────────────►
+                                          Shared Secret = kQ = kdG
+
+                               Decrypt using derived key from restored Shared Secret
+```
+