message: Update README.md
  Update setup section: libqt4-network is needed in addition to libqtgui4 (on current debian buster at least).
diff: @@ -87,7 +87,7 @@ with each other, with the help of a P2P network to check for double-spending.
  Setup
  ---------------------
  You need the Qt4 run-time libraries to run Bitcoin-Qt. On Debian or Ubuntu:
  - `sudo apt-get install libqtgui4`
  + `sudo apt-get install libqtgui4 libqt4-network`
  Unpack the files into a directory and run:
  