The main branch is no more than 5 commits ahead

[viktoriia-fomina]

Description

Now we check on PR if the current branch is no more than 5 commits behind the main branch. If it's not true, pipeline fails and the developer cannot merge into the main branch.

Fixes #491

Type of Change

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

How Has This Been Tested?

Automated Testing

Not applicable.

Manual Scenario

Checklist (remove irrelevant options):

• The change followed the style guidelines of the UTBot project
• Self-review of the code is passed
• The change contains enough commentaries, particularly in hard-to-understand areas
• New documentation is provided or existed one is altered
• No new warnings
• Tests that prove my change is effective
• All tests pass locally with my changes