async generateFromFile(asyncapiFile) {
    const doc = await readFile(asyncapiFile, { encoding: 'utf8' });
    return await this.generate(doc, { path: asyncapiFile });
  }
Generates files from a given template and AsyncAPI file.

@example
generator
  .generateFromFile('asyncapi.yaml')
  .then(() => {
    console.log('Done!');
  })
  .catch(console.error);

@example <caption>Using async/await</caption>
try {
  await generator.generateFromFile('asyncapi.yaml');
  console.log('Done!');
} catch (e) {
  console.error(e);
}

@param  {String} asyncapiFile AsyncAPI file to use as source.
@return {Promise<TemplateRenderResult|undefined>}