update readme

readme.md

@@ -1,7 +1,50 @@
 ![rayjs logo](./doc/logo.png)
 # rayjs - Javascript Bindings for Raylib
 Javascript bindings for raylib in a single ~3mb executable
+
+## What is this?
+rayjs is small ES2020 compliant Javascript interpreter based on [QuickJS](https://bellard.org/quickjs/) with bindings for [Raylib](https://www.raylib.com/). You can use it to develop desktop games with Javascript.
+
+## Features
+* Compiles into a single, small executable without any dependencies for easy distribution
+* Use modern Javascript features like classes or async/await
+* In-depth auto-complete with definitions for the whole API
+
+## Getting started
+1. Download the binary for your platform from the release section.
+2. Unzip the executable to a folder and create a new text file in the same folder. Rename the file to `main.js`
+3. Open the file with a text-editor (e.g. Notepad) and add the following code
+    ```javascript
+    const screenWidth = 800;
+    const screenHeight = 450;
+
+    initWindow(screenWidth, screenHeight, "raylib [core] example - basic window");
+
+    setTargetFPS(60);   
+    while (!windowShouldClose()) {
+        beginDrawing();
+
+            clearBackground(RAYWHITE);
+
+            drawText("Congrats! You created your first window!", 190, 200, 20, LIGHTGRAY);
+
+        endDrawing();
+    }
+    closeWindow();
+    ```
+4. Run the `rayjs` executable
+5. Congratulations, you have created your first rayjs app. 
+
+## Running code
+rayjs will run code in three different modes
+1. If no parameter is given it will look for a file called `main.js` in the executable directory
+2. It will run a given Javascript file given as a command line argument like this `rayjs <filename>`
+3. It will look for a file called `main.js` in a folder given as a command line argument like this `rayjs <foldername>`
+
+The directory of the main Javascript module will also be the working directory of the app. Modules and resources will be loaded relative to it.
+
 ## Building
+Here are some basic steps if you want to compile rayjs yourself:
 
 ### Check out required files
 ```bash
@@ -18,3 +61,7 @@ cd build
 cmake ..
 make
 ```
+
+## Performance
+QuickJS is one of the [faster JS interpreters](https://bellard.org/quickjs/bench.html). I'm getting about 13000 bunnys in bunnmark before dropping any frames on my 2020 Macbook Air M1 which seems pretty good.
+![Bunnymark](doc/bunny.png)