The micro:bit can transmit serial data via USB, radio and bluetooth. However, the DAPLink software loaded into the interface processor only supports mass storage class, communications device class, and HID for debug use. The daplink project is here:

There is no specific package or program to control a PC or simulate a keyboard press, but there are several projects that use the micro:bit as a remote that may be of interest if you are wanting to do this:

  1. Bluetooth MIDI package allows you to map micro:bit gestures to MIDI events, often used in music. 
  2. micro:bit + Spotify allows you to control your Spotify playlist
  3. The Bitio library for micropython allows yo to interact directly with the micro:bit and control programs like Minecraft