message: Add static & instance method examples to QSG
  quick-start-guide(gh-page): add example for static methods
  quick-start-guide(gh-page): add example for instance methods
  closes typegoose/typegoose#304
diff: @@ -132,3 +132,53 @@ Please note that `new Kitten({})` & `Kitten.create({})` has no types of KittenCl
  - Typegoose aims to get Mongoose's models to be stable through type-information
  - Typegoose aims to make Mongoose more usable by making the models more type-rich with TypeScript
  - Decorated schema configuration classes (like KittenClass above) must use explicit type declarations
  +
  +## Extra Examples
  +
  +### Static Methods
  +
  +Sometimes extra functions for model creation or pre-written querys are needed, they can be done as follows:
  +
  +```ts
  +class KittenClass {
  + @prop()
  + public name?: string;
  +
  + @prop()
  + public species?: string;
  +
  + public static async findBySpecies(this: ReturnModelType<typeof KittenClass>, species: string) {
  + return this.find({ species }).exec();
  + }
  +}
  +const KittenModel = getModelForClass(KittenClass);
  +
  +const docs = await KittenModel.findBySpecies("SomeSpecies");
  +```
  +
  +Note: pre-6.0 static functions needed `@staticMethod`, but this is not needed anymore
  +
  +### Instance Methods
  +
  +Sometimes extra functions for manipulating data on an instance is needed, they can be done as follows:
  +
  +```ts
  +class KittenClass {
  + @prop()
  + public name?: string;
  +
  + @prop()
  + public species?: string;
  +
  + public async setSpeciesAndSave(this: DocumentType<KittenClass>, species: string) {
  + this.species = species;
  + return await this.save();
  + }
  +}
  +const KittenModel = getModelForClass(KittenClass);
  +
  +const doc = new KittenModel({ name: "SomeCat", species: "SomeSpecies" });
  +await doc.setSpeciesAndSave("SomeOtherSpecies");
  +```
  +
  +Note: pre-6.0 instance functions needed `@instanceMethod`, but this is not needed anymore
  