Do not center table headers by default

[dviererbe]

The furo base theme centers table headers. This looks weird in my opinion for tables with only a few columns. See for example:

The source, so that you can play around with the style yourself:

+-------------------+--------------------+
| lorem             |  ipsum             |
+===================+====================+
| dolor             | sit                |
+-------------------+--------------------+
| amet              | consectetur        |
+-------------------+--------------------+
| adipiscing        | eli                |
+-------------------+--------------------+
| sed               | do                 |
+-------------------+--------------------+

Centering table headers with this change is still possible, for example:

.. role:: center
   :class: align-center

+-------------------+--------------------+
| :center:`lorem`   | :center:`ipsum`    |
+===================+====================+
| dolor             | sit                |
+-------------------+--------------------+
| amet              | consectetur        |
+-------------------+--------------------+
| adipiscing        | eli                |
+-------------------+--------------------+
| sed               | do                 |
+-------------------+--------------------+

This uses the style of table.align-center defined in custom.css:

sphinx-docs-starter-pack/.sphinx/_static/custom.css

Lines 29 to 32 in 1393e0b

	/* Allow to centre text horizontally in table data cells */
	table.align-center {
	text-align: center !important;
	}

[pmatulis]

I agree with having left-aligned table headers by default. Waiting a bit in case other TAs feel differently.

[s-makin]

Left-aligned by default would be my preference as well, the header should follow the column contents unless in specific cases.

Off the top of my head though, I don't think we have documented anywhere about these table options for the benefit of people who might not be as familiar with rst directives. I'll drop an approve on this because it's a good change, but it's worth also adding a note to the rst cheat sheet to show how to get centred header text.

[pmatulis]

Good point @s-makin , and I feel that we should make the cheat-sheet addition in this PR.

[ru-fu]

Looks good to me, but I agree that it needs an update to the cheat sheets (both RST and MyST).
We don't have this in the style guide at the moment - do we think it's needed in there?

[dviererbe]

Can this be merged?

[ru-fu]

I added two commits - one to fix a problem that it now wasn't possible anymore to centre a full table, and one to add examples to the cheat sheet.
Are you okay with these additions?

[dviererbe]

Looks good to me :)

Praise: Thanks for adding the center role to the rst_prolog and documenting it! I like that it is defined in custom_conf.py so that downstreams can remove or rename it if wanted/needed.