Is there a way to specify environment variables for netlify.toml for local development?

As I understand this file is required during build stage on netlify and needs to be included inside the GitHub repository, for example. But this way it's impossible to hide any environment variables, such as API keys.

Are there any ways similar to create-react-app where .env.local is used, but ignored via .gitignore.

After messing around I found a workaround by specifying a webpack.functions.js that picks up .env:

const Dotenv = require('dotenv-webpack')

// @see https://github.com/netlify/netlify-lambda#webpack-configuration
module.exports = {
  plugins: [new Dotenv()],
}

If this is the best way, then it could be useful mentioning this approach in the readme.