[ci] #4502: Enforce Conventional Commits in PR titles

[nxsaken]

Description

Enforce Conventional Commits style in PR titles.

Linked issue

Closes #4502.

Benefits

See here.

Checklist

• I've read CONTRIBUTING.md
• I've used the standard signed-off commit format (or will squash just before merging)
• All applicable CI checks pass (or I promised to make them pass later)
• (optional) I've written unit tests for the code changes
• I replied to all comments after code review, marking all implemented changes with thumbs up

[mversic]

We don't enforce issue numbers in the PR anymore. I think this is good for these reasons:

1. we shouldn't be putting issue numbers but rather PR numbers
2. if you use "squash and merge" button on github it adds PR number automatically
3. if you use "rebase and merge" then just add issue number manually to the end of your commit like github would do

Let's make sure that devs are notified of this change

[nxsaken]

CC recommends using footers for issue numbers:

fix(iroha_client_cli): ...

Refs: #issue_number

[mversic]

CC recommends using footers for issue numbers:

fix(iroha_client_cli): ...

Refs: #issue_number

yes, I know. I think the way github does it is quite convenient. Especially when generating content iroha-news or changelog. In that case I use git log --oneline to get a brief report of the commits and it's great to see PR issue numbers there instead of having to parse the body of the commit message