Tweak - Mailchimp and Mailerlite into module

[riteelama]

All Submissions:

• Have you followed the Everest Forms Contributing guideline?
• Does your code follow the WordPress' coding standards?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?

Changes proposed in this Pull Request:

We had the Mailerlite and Mailchimp integration with our plugin through the addons system Now, This PR adds the Mailerlite and Mailchimp integration as the feature.

Closes # .

How to test the changes in this Pull Request:

For Mailerlite:

1. Go to Everest Forms Dashboard> Features
2. Enable the Mailerlite
3. Click on the settings button it will redirect to the settings page for mailerlite and enter the API key and its nickname.
4. Please go through the steps provide in our previous Everest Forms Mailerlite documentation

For Mailchimp:

1. Go to Everest Forms Dashboard> Features
2. Enable the Mailchimp
3. Click on the settings button it will redirect to the settings page for mailchimp and enter the API key and its nickname.
4. Please go through the steps provide in our previous Everest Forms Mailchimp documentation

Note: Please also check the backward compatibility.
PR Dependency

Types of changes:

• Bug fix (non-breaking change which fixes an issue)
• Enhancement (modification of the currently available functionality)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Other information:

• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you successfully ran tests with your changes locally?
• Have you updated the documentation accordingly?

Changelog entry

Tweak - Mailchimp and Mailerlite into module

[NirajChaudhary143]

LGTM 👍

[joshianup1]

LGTM 👍