Documentation Site on GitHub Pages (#2376)

* Add initial documentations

* Update documentation for Basic Client and add WebSocket section

* feat: add a static site generator with multi-language support

- Introduced a new Rust-based static site generator in the `docs-gen` directory.
- Implemented core functionality for building sites from markdown files, including:
  - Configuration loading from `config.toml`.
  - Markdown rendering with frontmatter support.
  - Navigation generation based on page structure.
  - Static file copying and output directory management.
- Added templates for base layout, pages, and portal.
- Created a CSS file for styling and a JavaScript file for interactive features like language selection and theme toggling.
- Updated documentation source with new configuration and example pages in English and Japanese.
- Added a `justfile` target for building the documentation site.

* Add language/theme toggle functionality

- Created a new Japanese tour index page at docs/ja/tour/index.html
- Implemented navigation links for various sections of the cpp-httplib tutorial
- Added a language selector to switch between English and Japanese
- Introduced theme toggle functionality to switch between light and dark modes
- Added mobile sidebar toggle for better navigation on smaller screens

docs-src/pages/en/tour/08-websocket.md

@@ -0,0 +1,139 @@
+---
+title: "WebSocket"
+order: 8
+---
+
+cpp-httplib supports WebSocket as well. Unlike HTTP request/response, WebSocket lets the server and client exchange messages in both directions. It's great for chat apps and real-time notifications.
+
+Let's build an echo server and client right away.
+
+## Echo Server
+
+Here's an echo server that sends back whatever message it receives.
+
+```cpp
+#include "httplib.h"
+#include <iostream>
+
+int main() {
+    httplib::Server svr;
+
+    svr.WebSocket("/ws", [](const httplib::Request &, httplib::ws::WebSocket &ws) {
+        std::string msg;
+        while (ws.read(msg)) {
+            ws.send(msg);  // Send back the received message as-is
+        }
+    });
+
+    std::cout << "Listening on port 8080..." << std::endl;
+    svr.listen("0.0.0.0", 8080);
+}
+```
+
+You register a WebSocket handler with `svr.WebSocket()`. It works just like `svr.Get()` and `svr.Post()` from Chapter 3.
+
+Inside the handler, `ws.read(msg)` waits for a message. When the connection closes, `read()` returns `false`, so the loop exits. `ws.send(msg)` sends a message back.
+
+## Connecting from a Client
+
+Let's connect to the server using `httplib::ws::WebSocketClient`.
+
+```cpp
+#include "httplib.h"
+#include <iostream>
+
+int main() {
+    httplib::ws::WebSocketClient client("ws://localhost:8080/ws");
+
+    if (!client.connect()) {
+        std::cout << "Connection failed" << std::endl;
+        return 1;
+    }
+
+    // Send a message
+    client.send("Hello, WebSocket!");
+
+    // Receive a response from the server
+    std::string msg;
+    if (client.read(msg)) {
+        std::cout << msg << std::endl;  // Hello, WebSocket!
+    }
+
+    client.close();
+}
+```
+
+Pass a URL in `ws://host:port/path` format to the constructor. Call `connect()` to start the connection, then use `send()` and `read()` to exchange messages.
+
+## Text and Binary
+
+WebSocket has two types of messages: text and binary. You can tell them apart by the return value of `read()`.
+
+```cpp
+svr.WebSocket("/ws", [](const httplib::Request &, httplib::ws::WebSocket &ws) {
+    std::string msg;
+    httplib::ws::ReadResult ret;
+    while ((ret = ws.read(msg))) {
+        if (ret == httplib::ws::Binary) {
+            ws.send(msg.data(), msg.size());  // Send as binary
+        } else {
+            ws.send(msg);  // Send as text
+        }
+    }
+});
+```
+
+- `ws.send(const std::string &)` — sends as a text message
+- `ws.send(const char *, size_t)` — sends as a binary message
+
+The client-side API is the same.
+
+## Accessing Request Information
+
+You can read HTTP request information from the handshake through the first argument `req` in the handler. This is handy for checking authentication tokens.
+
+```cpp
+svr.WebSocket("/ws", [](const httplib::Request &req, httplib::ws::WebSocket &ws) {
+    auto token = req.get_header_value("Authorization");
+    if (token.empty()) {
+        ws.close(httplib::ws::CloseStatus::PolicyViolation, "unauthorized");
+        return;
+    }
+
+    std::string msg;
+    while (ws.read(msg)) {
+        ws.send(msg);
+    }
+});
+```
+
+## Using WSS
+
+WebSocket over HTTPS (WSS) is also supported. On the server side, just register a WebSocket handler on `httplib::SSLServer`.
+
+```cpp
+httplib::SSLServer svr("cert.pem", "key.pem");
+
+svr.WebSocket("/ws", [](const httplib::Request &, httplib::ws::WebSocket &ws) {
+    std::string msg;
+    while (ws.read(msg)) {
+        ws.send(msg);
+    }
+});
+
+svr.listen("0.0.0.0", 8443);
+```
+
+On the client side, use the `wss://` scheme.
+
+```cpp
+httplib::ws::WebSocketClient client("wss://localhost:8443/ws");
+```
+
+## Next Steps
+
+Now you know the basics of WebSocket. This wraps up the Tour.
+
+The next page gives you a summary of features we didn't cover in the Tour.
+
+**Next:** [What's Next](../09-whats-next)