Fix: Block content pulled through external connections get converted to classic

[dinhtungdu]

Description of the Change

• Add: A new helper function to detect if the current site is using Gutenberg or not.
• Fix: get correct content when pulling block-based posts through external connections.

See: #516 (comment)

Alternate Designs

n/a

Benefits

Better support for block editor.

Possible Drawbacks

n/a

Verification Process

0. Activate block editor/Gutenber on both sites.
1. Go to Distributor > Pull Content.
2. Choose the target external connection.
3. Pull a post that has blocks.
4. See the pulled post has identical content with block display correctly.

Checklist:

• I have read the CONTRIBUTING document.
• My code follows the code style of this project.
• [] My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my change.
• All new and existing tests passed.

Applicable Issues

Close #516

Changelog Entry

[adamsilverstein]

@dinhtungdu you might want to consider supporting VIP's ramp here if they are still using it: https://github.com/Automattic/gutenberg-ramp

[dinhtungdu]

@adamsilverstein Thanks for the heads up! I added support for Gutenberg Ramp. If you have time, please take a look : )

[dkotter]

@dinhtungdu Tested this and seems to work great! There are a few linting errors, so if you can get those cleaned up, I think this will be good to merge.

Edit: also seems some WPA tests are failing that we should fix up.