Added changelog changed validator

[JrooTJunior]

Description

In many cases contributors forget to add description of the changes to CHANGES/ directory, so we need to validate that automatically via GutHub Actions

Type of change

• New feature (non-breaking change which adds functionality)

How Has This Been Tested?

Via current pull-request

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[codecov]

Codecov Report

Merging #873 (1ec67d9) into dev-3.x (baf31a5) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##           dev-3.x      #873   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          284       284           
  Lines         7784      7784           
=========================================
  Hits          7784      7784           

Flag	Coverage Δ
unittests	100.00% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

[github-actions]

✔️ Changelog found.

Thank you for adding a description of the changes