docs(readme): add basic introduction

README.md

@@ -1 +1,31 @@
-# Cridium/Server
+# Cridium Server
+This is the server of Cridium, written in TypeScript with the [DeepKit](https://deepkit.io) framework.
+
+## How to debug
+### Prerequisites
+1. Git and Nodejs 16+ installed.
+2. `python3` and `build-essential` installed if you're on Linux, or follow [`node-gyp`'s guideline](https://github.com/nodejs/node-gyp#on-windows) if you're on Windows.
+
+### Steps
+1. Clone the repository, and install the dependencies
+
+```bash
+git clone https://github.com/Cridium/cridium-server.git --depth 1
+cd cridium-server
+npm install
+```
+
+If `npm install` fails, recheck step 2 in prerequisites.
+
+2. Copy the example configuration file `.env.example` to `.env` and modify the following
+
+```
+APP_FRAMEWORK_DEBUG=true
+```
+
+3. Run `npm run dev`
+
+And it's running! Go to your browser and open `http://localhost:8080/_debug`(on WSL, you can see the hostname by executing `hostname -I`), you'll see the DeepKit Debugger.
+
+## License
+Apache License 2.0