feat/193: add a previewer in admin settings

[Sidsector9]

Description of the Change

This PR adds a feature to display preview of the taxonomy types for a post.

1. Adds a select dropdown with AJAX-based search input field to select/search a post.
2. Displays the score/relevance and the label in results.
3. Displays color-based bar with a width indicating score for visual clarity.

Closes #193

Screencast

Classifai.mov

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.

Changelog Entry

Added - Preview for Language Processing settings changes

Credits

Props @Sidsector9

[Sidsector9]

@jeffpaul What title should we add to the previewer? Also wanted your opinion on the results, is there anything we would want to add/remove in this implementation?

[jeffpaul]

What title should we add to the previewer?

How about Preview Language Processing?

Also wanted your opinion on the results, is there anything we would want to add/remove in this implementation?

It might help to show placeholders for the Categories, Keywords, Entities, and Concepts sections where data eventually gets returned/rendered so that section doesn't suddenly jump down when the data's ready?

[iamdharmesh]

Thanks a lot for the great work here @Sidsector9. Overall code looks good to me, just added a few minor comments to check.
Also, please help to add title as mentioned here #351 (comment)

Thanks

[Sidsector9]

Empty placeholders added:

With results populated:

[iamdharmesh]

LGTM! 🚀 Thanks for great work here @Sidsector9