code: def watch(ctx):
      
      watcher = Watcher(ctx)
      watcher.watch_directory(
          path='{pkg.source_less}', ext='.less',
          action=lambda e: build(ctx, less=True)
      )
      watcher.watch_directory(
          path='{pkg.source_js}', ext='.jsx',
          action=lambda e: build(ctx, js=True)
      )
      watcher.watch_directory(
          path='{pkg.docs}', ext='.rst',
          action=lambda e: build(ctx, docs=True)
      )
      watcher.start()
docs: Automatically run build whenever a relevant file changes.