Table Block: Add Border Colors

[CreativeDive]

If the table block has a border, the border color assigned to the background color can not be changed at this time. The table borders are thus without contrast for tables with background color:

To solve this issue, an additional color selection for the border color would be necessary.

Also a custom color selection for the table background color would be great. At this time only four fix colors are possible.

[karmatosed]

Over adding yet another section, one option for this could be to contrast change the border depending on the backgrounds set. This could get complicated with multiple ones but they are all more or less on the same level, so I think it could work.

The above said I think as tables are expanded in functionality having a way to colour borders could be something people want.

[ChemicalSailor]

Related: #16478

[melchoyce]

Instead of a border color selector, could we instead automatically generate a better border color by darkening the background colors? We already seem to be doing that for the color select borders:

[karmatosed]

I think that's a great plan @melchoyce, let's move this into needs dev.

[javierarce]

I think we can close this issue since we already support border settings per this PR: #31265