Add support for Patchstack API

[iamdharmesh]

Description of the Change

As requested in #70, this PR adds support for Patchstack API to check reported vulnerabilities for WordPress core, installed plugins and themes.

Users can choose Patchstack API for vulnerabilities scan by adding VULN_API_PROVIDER constant in wp-config.php. By default, the current WPScan API service will be used.

define( 'VULN_API_PROVIDER', 'patchstack' );

Closes #70

How to test the Change

1. Add a VULN_API_PROVIDER constant in wp-config.php as below.

   define( 'VULN_API_PROVIDER', 'patchstack' );

2. Add a VULN_API_TOKEN constant in wp-config.php by getting API key from patchstack.com

   define( 'VULN_API_TOKEN', 'YOUR_TOKEN_HERE' );

3. Try given vuln commands in readme to scan for vulnerabilities.
4. Make sure all commands are working fine.
5. Make sure all commands are working fine with both services (WPScan and Patchstack)

Changelog Entry

Added - Support for Patchstack API

Credits

Props @iamdharmesh, @MARQAS, @dkotter, @jeffpaul.

Checklist:

• [x] I agree to follow this project's Code of Conduct.
• [x] I have updated the documentation accordingly.
• [ ] I have added tests to cover my change.
• [ ] All new and existing tests pass.

[dkotter]

@iamdharmesh Code here looks good to me. I spent some time to see if I could get tests to run but I had no luck. If everything else is working here, I'd suggest we comment out the Github Action (so we don't have failing actions on any new PRs), merge this in and then work on fixing the tests in a separate PR /cc @jeffpaul