Format table cells

Asciidoctor supports formatting of single cells. See Asciidoctor User Manual, section cell formatting.

It would be nice to have a context menu to format the current cell. Partial support for the options is fine as long as existing elements are unchanged.

To support this the lexer/parser would need to learn how to treat tables.

[cols="3"]
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^|Prefix the `{vbar}` with `{caret}` to center content horizontally
<|Prefix the `{vbar}` with `<` to align the content to the left horizontally
>|Prefix the `{vbar}` with `>` to align the content to the right horizontally

.^|Prefix the `{vbar}` with a `.` and `{caret}` to center the content in the cell vertically
.<|Prefix the `{vbar}` with a `.` and `<` to align the content to the top of the cell
.>|Prefix the `{vbar}` with a `.` and `>` to align the content to the bottom of the cell

3+^.^|This content spans three columns (`3{plus}`) and is centered horizontally (`{caret}`) and vertically (`.{caret}`) within the cell.

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