Support colspan and rowspan

[glittershark]

Reactable should support table cells with colspan and rowspan. We need to figure out how these cells are filtered and sorted, how they're displayed when one but not all of the related rows are present, etc.

See #83 for the original impetus for this.

[gregeinfrank]

@glittershark I'm trying to include a full-width <tfoot> at the bottom of the Table, but it seems impossible right now. I think colspan of 0 is the only way to do it right?

[javflores]

Hi @glittershark is colSpan supported already in Reactable?
If not maybe I can help moving that pull request by @paulcameron move forward: #135

[wojciech-skowronek]

@glittershark What about that feature? I have the same issue like @gregeinfrank over one year ago.

[GuillaumeCisco]

Yep, What about this feature?
It is very interesting and needed!
@glittershark

[rizkiandrianto]

+1 we need it to this beautiful table

[stclairdaniel]

+1 to this!