Hot to add 'text' indexes

[OmarOmeiri]

Counld not find in the docs a way to add text indexes like you could do with mongoose.
like this:

const mongoose = require('mongoose');
const UserSchema = new mongoose.Schema({

  email: {
    type: String,
    required: true,
  },
  fname: {
    type: String,
    required: true,
  },
  lname: {
    type: String,
    required: true,
  },
});

UserSchema.index({ email: 'text' });
module.exports = User = mongoose.model('user', UserSchema);