MongoDB connection with SSL

For anybody that's looking to connect to a database with SSL, I got it to work by modifying `agendash-standalone.js`.
Replace line 21 with:
```
const certFileBuf = fs.readFileSync(
  "mycert.pem"
);
const agenda = new Agenda({
  db: {
    address: program.db,
    collection: program.collection,
    options: {
      sslCA: certFileBuf,
    },
  },
});
```