docs: Efl.Ui.Table_Static

The need for this class is still being discussed in
https://phab.enlightenment.org/T8206
but at least it is a bit more clear what its purpose is.

src/lib/elementary/efl_ui_table_static.eo

@@ -1,6 +1,12 @@
 class @beta Efl.Ui.Table_Static extends Efl.Ui.Table
 {
-   [[Efl UI table static class]]
+   [[Widget container that arranges its elements in a uniform grid.
+
+     For convenience, the grid has an initial size of 100 by 100 cells, so all positions and
+     sizes can be interpreted as percentages.
+     Cells are always shown with the same size, regardless of their content. Therefore, adding
+     content to one cell does not affect other cells.
+   ]]
    data: null;
    implements {
       Efl.Object.constructor;