docs: added README.md and flow chart

README.md

@@ -1,3 +1,30 @@
 # error-express-handler
 
-error-express-handler
+This package exports a middleware for express that handles Error and HttpError(custom package type).
+## Install
+```sh
+npm install --save @map-colonies/error-express-handler
+```
+
+## Usage
+
+
+```ts
+import express from 'express';
+import { getErrorHandlerMiddleware } from '@map-colonies/error-express-handler';
+
+process.env.NODE_ENV = 'development';
+
+const app = express();
+
+app.use('/meow', fn);
+
+app.use(getErrorHandlerMiddleware((message) => console.error(message)));
+
+app.listen(8080, function() {
+    console.log('server is up');
+});
+```
+
+## Flow
+![Flow of package](docs/flow.png)