Drupal 10 & 11 compatability

Hey, your progress on this issue looks amazing, but can you please split your changes to several issues/MRs, because it's difficult to review.
PHPCS fixes and Readme, Changelog changes can be moved to separate issue.
And there are several issue with similar changes:

• 📌 Replace README.txt with README.md RTBC
• 📌 Add gitlab CI Active

I found the reason why migrate tests fails.
[#2205327]

Added changes to MR 13.
And created Draft MR 14, to check if tests will pass with minimal code changes.

nikolay shapovalov → changed the visibility of the branch 3493996-migrate-fix to hidden.

I run phpstan inspection on level 5 for MR 13.
Created new branch 3493996-drupal-10--phpstan-5, you can check changes at commit e1149d4.