Improved welcome intent

index.ts

app.intent('Default Welcome Intent', async (conv: Conv) => {
  conv.ask(new SimpleResponse({
    text: 'Welcome to Tabletop Audio! I can play a specific track, ' +
      'or start playing based on a genre. What do you want to listen to?',
    speech: `Welcome to Tabletop Audio! I can play a specific track ` +
      `like ${conv.data.json.tracks[0].track_title}, or start playing based on a genre like ` +
      `${conv.data.json.tracks[0].track_genre}. What do you want to listen to?`
  }))
  conv.ask(getSuggestions(conv.data.json.tracks))
})