message: Add new query methods
  hooks(src): add "countDocuments" and "estimatedDocumentCount" as QueryMethod
  This is a squash merge of typegoose/typegoose#324
diff: @@ -32,7 +32,7 @@ type DocumentMethod = 'init' | 'validate' | 'save' | 'remove';
  type NumberMethod = 'count';
  type SingleMethod = 'findOne' | 'findOneAndRemove' | 'findOneAndUpdate' | DocumentMethod;
  type MultipleMethod = 'find' | 'update';
  -type QueryMethod = 'count' | 'find' | 'findOne' | 'findOneAndRemove' | 'findOneAndUpdate' | 'update' | 'updateOne' | 'updateMany';
  +type QueryMethod = 'count' | 'countDocuments' | 'estimatedDocumentCount' | 'find' | 'findOne' | 'findOneAndRemove' | 'findOneAndUpdate' | 'update' | 'updateOne' | 'updateMany';
  type ModelMethod = 'insertMany';
  type QMR = QueryMethod | ModelMethod | RegExp;
  type QDM = QMR | DocumentMethod;
  