* Add guide on adding support for variable queries

* Fix review comments

* Update instruction for custom editor

* Update docs/sources/developers/plugins/add-support-for-variables.md

Co-authored-by: Alexander Zobnin <alexanderzobnin@gmail.com>

* Update docs/sources/developers/plugins/add-support-for-variables.md

Co-authored-by: Diana Payton <52059945+oddlittlebird@users.noreply.github.com>

* Update docs/sources/developers/plugins/add-support-for-variables.md

Co-authored-by: Diana Payton <52059945+oddlittlebird@users.noreply.github.com>

* Fix review comments

* Fix review comments

Co-authored-by: Alexander Zobnin <alexanderzobnin@gmail.com>
Co-authored-by: Diana Payton <52059945+oddlittlebird@users.noreply.github.com>