feat: update

README.md

@@ -1,3 +1,46 @@
 # acme-client-rs
 
-ACME Client in Rust
+ACME Client in Rust
+
+Acme client help:
+```shell
+$ acme-client --help
+acme-client 0.3.0
+Hatter Jiang <jht5945@gmail.com>
+Acme auto challenge client, acme-client can issue certificates from Let's encrypt
+
+USAGE:
+    acme-client [FLAGS] [OPTIONS]
+
+FLAGS:
+        --check        Check cert config
+    -h, --help         Prints help information
+        --hide-logo    Hide logo
+    -v, --verbose      Verbose
+    -V, --version      Print version
+
+OPTIONS:
+    -a, --algo <algo>           Pki algo [default: ec384]
+    -c, --config <config>       Cert config
+        --dir <dir>             Account key dir [default: acme_dir]
+    -d, --domain <domain>...    Domains
+        --email <email>         Contract email
+    -m, --mode <mode>           Mode [default: prod]
+    -p, --port <port>           Http port [default: 80]
+        --timeout <timeout>     Timeout (ms) [default: 5000]
+    -t, --type <type>           Type http or dns [default: http]
+```
+
+签发一张证书示例
+* 先将域名指向对应的服务器，保证服务器上的 `80` 端口可被互联网访问
+* `acme-client --email your-email@example.com --domain your-domain.example.com`
+
+使用参数 `--config` 时的配置文件示例:
+```json
+{
+  "certItems": [{
+    "path": "dir_cryptofan_org",
+    "dnsNames": ["cryptofan.org", "www.cryptofan.org"]
+  }]
+}
+```