feature: sort rows by column value

[zoranjovo]

Addresses #292

Simply adds arrows next to each column name to sort all rows by that value asc or desc. Same as how the actual dynamodb web client can reorder rows just on the visible data currently displayed.

[rchl]

I haven't tried it but given that it works on the client side, I assume it only takes into account items on the current page? That would likely not be good enough since user would expect that all the data is in sorted order and not only the current page.

[zoranjovo]

Yep that's right, the user would need to set the page size to a high enough value to have all the data being shown to be able to sort it all. This is the same as how dynamodb > explore items on the aws console works. To have it rescan the entire table then sort would probably be beyond my knowledge.

Also I realised that on my version of macOS the Unicode arrows I chose don't render properly so I will fix that since I made this on a windows desktop.