message: added documentation for plugins
diff: @@ -327,15 +327,24 @@ Of course `this` is not the document in a post hook (see Mongoose docs). Again t
  #### plugin
  -Using the `plugin` decorator enables the developer to attach various Mongoose plugins to the schema. Just like the regular `schema.plugin()` call, the decorator accepts 1 or 2 parameters: the plugin itself, and an optional configuration object.
  +Using the `plugin` decorator enables the developer to attach various Mongoose plugins to the schema. Just like the regular `schema.plugin()` call, the decorator accepts 1 or 2 parameters: the plugin itself, and an optional configuration object. Multiple `plugin` decorator can be used for a single Typegoose class.
  If the plugin enhances the schema with additional properties or instance / static methods this typing information should be added manually to the Typegoose class as well.
  -```
  +```typescript
  +import * as findOrCreate from 'mongoose-findorcreate';
  +
  @plugin(findOrCreate)
  class User extends Typegoose {
  -
  + // this isn't the complete method signature, just an example
  + static findOrCreate(condition: InstanceType<User>):
  + Promise<{ doc: InstanceType<User>, created: boolean }>;
  }
  +
  +const UserModel = new User().getModelForClass(User);
  +UserModel.findOrCreate({ ... }).then(findOrCreateResult => {
  + ...
  +});
  ```
  ### Types
  