chore: Added expect lib, updated readme

Author: roman.vasilev

README.md

@@ -1,4 +1,34 @@
 # errorlings
+Common errors for your application.
+
+## API
+Create error (all parameters optional and can be passed in any order)
+```ts
+const e = new CustomEror(status: number, message: string, code: string, inner: Error, { data: any });
+```
+Rules of detecting type of parameter:
+* typeof number: status
+* first string: message
+* second string: code
+* instanceof Error: inner
+* object with key data: data
+
+Using options object as parameter:
+```ts
+const err = new CustomEror({
+    status?: number;
+    data?: any;
+    code?: string;
+    inner?: Error;
+    message?: string;
+});
+```
+
+### Error classes and defaults
+* `ExceptionError`
+* `ForbiddenError` (status: 403, message: You don't have permission to do that.)
+* `NotFoundError` (status: 404)
+* `ValidationError` (status: 400)
 
 ## Changelog
 See [CHANGELOG.md](CHANGELOG.md)