Add an ONS table block

[zerolab]

What is the context of this PR?

This PR adds:

• a new table block using TinyMCE limited to the table plugin
• an ONS Table Block with source/footer notes

Screen recording

To-Do:

• integration test that adds a table and checks the output

How to review

Check the branch out, add/edit a statistical artcile/ methodology page.

Follow-up Actions

• Package and open source TinyTableBlock - https://github.com/torchbox/wagtail-tinytableblock/

[MebinAbraham]

Done an initial pass, this looks really good. Open sourcing TinyTableBlock 🎉 👍

• The Row header option does not work as expected when using the UI buttons. It works as expected when copying/pasting, but it does not "understand" that we have row headers and the icon is not highlighted. The column header is working as expected.
• We should add functional tests to validate the table behaviours. I feel like there are a few gaps that we don't test. We should test the different functionality and conditional cases such as each element is rendered if input, such as title, caption etc.
• There is an alignment issue with the table/page. It is indented too much. See attached image:

[zerolab]

There is an alignment issue with the table/page. It is indented too much. See attached image

That is because I wrapped the whole output in a figure element. Will change to a div

[zerolab]

@MebinAbraham I've re-tagged you. Will shortly switch to using the PyPI package for TinyTableBlock, but I think the changes are worth checking here

[sanjeevz3009]

Minor comments. LGTM! Will approve once the changes in progress are complete and I re-review =)

[MebinAbraham]

Typo, hides the invalid param use.

Suggested change

	{% set headers = params.headers if params.headers else parms.ths|list %}
	{% set headers = params.headers if params.headers else params.ths|list %}

[MebinAbraham]

• The Row header option does not work as expected when using the UI buttons. It works as expected when copying/pasting, but it does not "understand" that we have row headers and the icon is not highlighted. The column header is working as expected.

This still seems to be outstanding.

Also, I feel like there are still gaps in the test. We should have confidence in the features TinyMCE provide such as merged cells, row headers, column headers etc. For headers, we have tests that validate the value is displayed but not whether it is syntactically correct. At the moment, we don't validate the rendered version for things like merged cells, row headers, column headers etc.

Other than some gaps in tests, LGTM 👍