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/01-getting-started.md

@@ -0,0 +1,88 @@
+---
+title: "Getting Started"
+order: 1
+---
+
+All you need to get started with cpp-httplib is `httplib.h` and a C++ compiler. Let's download the file and get a Hello World server running.
+
+## Getting httplib.h
+
+You can download it directly from GitHub. Always use the latest version.
+
+```sh
+curl -LO https://github.com/yhirose/cpp-httplib/raw/refs/tags/latest/httplib.h
+```
+
+Place the downloaded `httplib.h` in your project directory and you're good to go.
+
+## Setting Up Your Compiler
+
+| OS | Development Environment | Setup |
+| -- | ----------------------- | ----- |
+| macOS | Apple Clang | Xcode Command Line Tools (`xcode-select --install`) |
+| Ubuntu | clang++ or g++ | `apt install clang` or `apt install g++` |
+| Windows | MSVC | Visual Studio 2022 or later (install with C++ components) |
+
+## Hello World Server
+
+Save the following code as `server.cpp`.
+
+```cpp
+#include "httplib.h"
+
+int main() {
+    httplib::Server svr;
+
+    svr.Get("/", [](const httplib::Request&, httplib::Response& res) {
+        res.set_content("Hello, World!", "text/plain");
+    });
+
+    svr.listen("0.0.0.0", 8080);
+}
+```
+
+In just a few lines, you have a server that responds to HTTP requests.
+
+## Compiling and Running
+
+The sample code in this tutorial is written in C++17 for cleaner, more concise code. cpp-httplib itself can compile with C++11 as well.
+
+```sh
+# macOS
+clang++ -std=c++17 -o server server.cpp
+
+# Linux
+# `-pthread`: cpp-httplib uses threads internally
+clang++ -std=c++17 -pthread -o server server.cpp
+
+# Windows (Developer Command Prompt)
+# `/EHsc`: Enable C++ exception handling
+cl /EHsc /std:c++17 server.cpp
+```
+
+Once it compiles, run it.
+
+```sh
+# macOS / Linux
+./server
+
+# Windows
+server.exe
+```
+
+Open `http://localhost:8080` in your browser. If you see "Hello, World!", you're all set.
+
+You can also verify with `curl`.
+
+```sh
+curl http://localhost:8080/
+# Hello, World!
+```
+
+To stop the server, press `Ctrl+C` in your terminal.
+
+## Next Steps
+
+Now you know the basics of running a server. Next, let's look at the client side. cpp-httplib also comes with HTTP client functionality.
+
+**Next:** [Basic Client](../02-basic-client)