Development/documentation (#1825)

* [docs] : add 'guidelines' in 'plugins/interfaces'

* [Documentation] small update

* [doc] add practical part 1

* [doc] small fixes to new guideliness section

* [doc] add queryinterface example to practicalities section

* [doc] add more sections to interface guideliness

* [doc] fix interface guidelines links

* [doc] update interface guideliness after review P. Wielders

* [Documentation] Update interface guideliness

* [doc] move files to assets

* [docs] : add WebSocket protocol

* [docs] : add introduction to 'websocket.md'

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Co-authored-by: Marcel Fransen <[email protected]>
Co-authored-by: MFransen69 <[email protected]>