335 add gutenberg to the list of editors a pr should be tested on

[FAMarfuaty]

Context

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Summary

This PR can be summarized in the following changelog entry:

• Adapts GitHub PR template to include Gutenberg to the list of editors a PR should be tested on and adds examples of documentation.

Relevant technical choices:

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Test instructions

Test instructions for the acceptance test before the PR gets merged

This PR can be acceptance tested by following these steps:

• N/A

Relevant test scenarios

• [ ] Changes should be tested with the browser console open
• [ ] Changes should be tested on different posts/pages/taxonomies/custom post types/custom taxonomies
• [ ] Changes should be tested on different editors (Block/Classic/Elementor/other)
• [ ] Changes should be tested on different browsers
• [ ] Changes should be tested on multisite

Test instructions for QA when the code is in the RC

• [ ] QA should use the same steps as above.

QA can test this PR by following these steps:

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Impact check

This PR affects the following parts of the plugin, which may require extra testing:

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UI changes

• [ ] This PR changes the UI in the plugin. I have added the 'UI change' label to this PR.

Documentation

• [ ] I have written documentation for this change.

Quality assurance

• [ ] I have tested this code to the best of my abilities
• [ ] I have added unittests to verify the code works as intended

Innovation

• [ ] No innovation project is applicable for this PR.
• [ ] This PR falls under an innovation project. I have attached the innovation label and noted the work hours.

Fixes #