- Fixes: `set-lookup-handlers!` couldn't define :definition or
:references handlers in text-mode derivatives.
- Adds: support for evaluating code in jupyter blocks (#2477).
With this, gr and gR will now work in babel blocks to execute a subset
of the block (or the whole thing, if you'd like). Results are displayed
in a popup buffer (or overlay if :tools (eval +overlay) is enabled).
