Add a dryrun mode for development

[doug-wade]

I've been doing some development on a bot, and I don't want to post my in-progress threads to a live, production lemmy instance. I'd prefer to be able to set the bot to be in "dry run" mode, and only log to the console the actions it would have taken on the production instance

The new option would be used as follows

const bot = new LemmyBot.LemmyBot({
  enableLogs: true,
  dryRun: true
});