Modified to support multiple project keys

[kamesh-09]

Currently the action supports only one project key.
Added support so multiple keys can be configured for PR title.
All keys can be defined on new lines, for eg:

 name: Enforce Jira Issue Key in Pull Request Title
  uses: ryanvade/enforce-pr-title-style-action@v2
  with:
    projectKeys: | 
      'AB'
      'CD'
      'EF'
    separator: ':'

Added new test cases and modified existing one.
This is a Breaking Change since projectKey is now renamed as projectKeys

[ryanvade]

Hey @kamesh-09 thank you for your PR. Before merging the changes in I would like to see a few changes made. First, I think the overall goal of this PR can be achieved without adding a breaking change.

Lets keep the use of projectKey while also adding the new projectKeys option that way existing users of this action can upgrade without issue.

Second, since this PR adds a new configuration option please make sure to update the README with documentation on how the new feature works.

Let me know if you want me to add these changes.

[kamesh-09]

Hi @ryanvade thanks for the feedback
I removed the older one in order to remove the redundancy, since projectKey and projectKeys will solve same purpose. But I got your point. I will add these changes, will also add this new feature in README.

[kamesh-09]

Removed the breaking changes and added new test cases around the projectKeys. Also, updated the README. If anything missing, please add.