Add support link for Premium users

[HardeepAsrani]

All Submissions:

• Have you followed the Optimole 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:

This adds a support button to the Sidebar if you view the plugin dashboard as a premium user and autofills the contact form on the website.

Closes #754.

How to test the changes in this Pull Request:

1. Connect to Optimole using a non-free account.
2. You should see a support button in the Optimole dashboard sidebar.
3. Clicking on it should load the contact page on the Optimole website with the details pre-filled.

Other information:

• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your changes, as applicable?
• Have you successfully ran tests with your changes locally?

[pirate-bot]

Plugin build for 0789770 is ready 🛎️!

• Download build

[rodica-andronache]

@HardeepAsrani everything's working well 👍

[pirate-bot]

🎉 This PR is included in version 3.8.2 🎉

The release is available on GitHub release

Your semantic-release bot 📦🚀