add beaker bindings to terarium notebooks

[blanchco]

Description

• Adding beaker keybindings to terarium notebook
  j, ArrowUp -> select previous cell
  k, ArrowDown -> select next cell
  a -> add cell above
  b -> add cell below
  enter -> enter cell
  esc -> exit cell

• fix: default dataset cell when opening notebook

[shawnyama]

getting some overflow issue

[blanchco]

getting some overflow issue

Hmmm, not really getting anything different on my side, I didnt really touch the css or templating. Let me see if I can create something similar

[blanchco]

The overflow issue was present before these changes, will fix this up when Im working on the cells