pandoc grid tables support

[mipmip]

Request to support reading and writing pandoc grid tables syntax.

 +---------------+---------------+
 | Fruit         | Price         |
 +===============+===============+
 | Bananas       | $1.34         |
 +---------------+---------------+
 | Oranges       | $2.10         |
 +===============+===============+
 | Sum           | $3.44         |
 +===============+===============+

More information about this syntax can be found on the pandoc website in paragraph 8.9.4

It could be implemented just like sc-im supports markdown tables read/write.