First prototype of a TiddlySheet

Nothing fancy to start.

Just setup TiddlyWiki / HTML / CSS code to pull together a simple table, along with simple structure to show mock-up of buttons to add columns and add rows to a tiddly sheet.

Tentative plan is to eventually have ability to toggle between various modes, like "view", "data editing" (to just edit content), and "table editing" (to adjust the table in whatever way, including adding columns, adding rows, swapping cells in the sheet).  Something lke that.