Doc: added new to expression documentation

[abey79]

Description

This commit documents the changes introduced in #498

Checklist

• feature/fix implemented
• code formatting ok (black and isort)
• mypy returns no error
• tests added/updated and pytest succeeds
• documentation added/updated
  • command docstring and option/argument help
  • README.md updated (Feature Overview)
  • CHANGELOG.md updated
  • added new command to reference.rst
  • RTD doc updated and building with no error (make clean && make html in docs/)

[sonarqubecloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
No Duplication information

[codecov]

Codecov Report

Merging #508 (280970f) into master (f342882) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #508   +/-   ##
=======================================
  Coverage   94.69%   94.69%           
=======================================
  Files          62       62           
  Lines        5631     5631           
  Branches      810      810           
=======================================
  Hits         5332     5332           
  Misses        182      182           
  Partials      117      117           

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