feat: add cert-watch example

https-tls/cert-watch/README.md

@@ -0,0 +1,38 @@
+# HTTPS Server With TLS Cert/Key File Watcher
+
+## Usage
+
+### Certificate
+
+We put the self-signed certificate in this directory as an example but your browser would complain that it isn't secure. So we recommend to use [`mkcert`] to trust it. To use local CA, you should run:
+
+```sh
+mkcert -install
+```
+
+If you want to generate your own cert/private key file, then run:
+
+```sh
+mkcert -key-file key.pem -cert-file cert.pem 127.0.0.1 localhost
+```
+
+### Running The Example Server
+
+```console
+$ cd https-tls/cert-watch
+$ cargo run
+starting HTTPS server at https://localhost:8443
+```
+
+Reload the server by modifying the certificate metadata:
+
+```console
+$ touch cert.pem
+```
+
+### Client
+
+- cURL: `curl -v --insecure https://127.0.0.1:8443`
+- Browser: go to <https://127.0.0.1:8443>
+
+[`mkcert`]: https://github.com/FiloSottile/mkcert