doc: add basic readme

Signed-off-by: Tony Gorez <gorez.tony@gmail.com>

README.markdown

@@ -1 +1,78 @@
-![IncludeJS](./assets/banner.png)
+<p align="center"><img src="./assets/banner.png" alt="includejs logo"/></p>
+<h1 align="center">includejs</h1>
+<h3 align="center">Build your own JavasScript runtime</h3>
+<p align="center">
+  <a href="https://github.com/crossnx/includejs/actions/workflows/ci.yml"><img src="https://github.com/crossnx/includejs/actions/workflows/ci.yml/badge.svg" alt="github action build"></a>
+</p>
+
+`includejs` aims to provide an unified API to build your own JavaScript runtime.
+
+## Features
+
+- Multiple runtime support: `JavascriptCore`, `v8` (more in the furture)
+- Cross platform support
+- Direclty consumable from `CMake`
+
+> Note: These lists are not exhaustive, we'll add new items very soon.
+
+### JavasScript
+
+| Feature        | JavaScriptCore    | V8               |
+|----------------|-------------------|------------------|
+| Boolean        | ✅ Supported      | ❌ Not Supported |
+| Number         | ✅ Supported      | ❌ Not Supported |
+| String         | ✅ Supported      | ❌ Not Supported |
+| Object         | ✅ Supported      | ❌ Not Supported |
+| Array          | ✅ Supported      | ❌ Not Supported |
+| Promise        | ✅ Supported      | ❌ Not Supported |
+| Function       | ✅ Supported      | ❌ Not Supported |
+| Error          | ✅ Supported      | ❌ Not Supported |
+| Class          | ❌ Not Supported  | ❌ Not Supported |
+| Set            | ❌ Not Supported  | ❌ Not Supported |
+| Map            | ❌ Not Supported  | ❌ Not Supported |
+| BigInt         | ❌ Not Supported  | ❌ Not Supported |
+| Symbol         | ❌ Not Supported  | ❌ Not Supported |
+| ArrayBuffer    | ❌ Not Supported  | ❌ Not Supported |
+| TypedArray     | ❌ Not Supported  | ❌ Not Supported |
+
+### WHATWG APIs
+
+- [ ] Timers
+- [ ] Console
+
+### Platform support
+
+| Platform  | JavaScriptCore    | V8               |
+|-----------|-------------------|------------------|
+| macOS     | ✅ Supported      | ✅ Supported     |
+| Linux     | ✅ Supported      | ✅ Supported     |
+| Windows   | ❌ Not Supported  | ❌ Not Supported |
+
+## Dependencies
+
+- C++
+- CMake
+- JavascriptCore
+- Brew (macOS)
+
+## Usage
+
+You can consume `includejs` just with CMake:
+
+```cmake
+cmake_minimum_required(VERSION 3.18)
+
+project(your_runtime VERSION 0.0.1 LANGUAGES CXX)
+
+include(FetchContent)
+FetchContent_Declare(
+  includejs
+  GIT_REPOSITORY https://github.com/crossnx/includejs
+  GIT_TAG        main
+  DOWNLOAD_EXTRACT_TIMESTAMP NO)
+FetchContent_MakeAvailable(includejs)
+
+add_executable(your_runtime main.cc)
+target_link_libraries(your_runtime PRIVATE includejs::engine)
+```
+