adjust 2d reader so the keyword has its own source location
and is syntax-original?
added a keybinding to center a line within its cell in a table
improve the way the font size callbacks work, wrt to interactivity
properly compose readtables
Make vector-set! type correctly on complicated inputs.

Closes PR13532.
Add checks for failing to parse types.
document c:x;r;c
add various dots to tex-table and thus drracket keyboard shortcuts
Adjusted a literal scribble tabular to use 2d
an attempt at 2d documentation
forgot to add tabular.rkt
Fix with-contract when the contracted identifier is defined as syntax.
Look for defines and handle them directly.

Since keyword definitions expand into multiple defines, and inserting
the contract and external id definitions at the wrong point will cause
those to break, we handle define manually.

Hat-tip to Vincent for the idea.

Doing this means that we can't put a single splicing-syntax-parameterize
around the entire body, since it'll expand defines before we reach them,
so instead we add them around the expanded code.
Tests for define/contract and keyword interaction.