fix: Fix IsValidMessage method adding a new exception for merge from master to the branch.

[esequielvirtuoso]

What?

[Here goes your feature/bug-fix proposal](fix: Fix IsValidMessage method adding a new exception for merge from master to the branch.)

Type of change?

• [fix]: A bug fix

Why?

Avoid commit-lint breaking when it's a merge from the master to the developer branch.

How?

Addin a new function to identify the merge action within the commit message.

How has this been tested?

• Unit tests

Before submitting a PR please make sure to check if:

• The code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented on my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• The changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and/or existing unit tests pass locally with my changes
• New and/or existing integration tests pass locally with my changes

[ebbauer]

LGTM