documentation

Pull request #289: [ZBX-19384] formatting code properly

Merge in WEB/documentation from feature/ZBX-19384-6.4-D to release/6.4

* commit '9e518eb540b3564cdfc6e551282b279919972909':
  [ZBX-19384] trying to fix bash example
  [ZBX-19384] multiline examples
  [ZBX-21195] python3 compatible header
  [ZBX-19384] note on reserved value without compression
  [ZBX-19384] formatting code properly