Use standard markdown table format

[killermoehre]

• Description of changes:

Markdown tables with all necessary sides set render prettier, as there is no ambiguity about the cell content and the border.

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[eemeli]

In this case, the style recommended by Prettier is not in fact prettier. Forcing the columns to match the longest contents makes them significantly longer and therefore line-wraps them, reducing the legibility of the source.

Also, the resulting HTML is the same, so this has no effect on the published spec.