Selection of injections via textobjects

[carrascomj]

#2311 is a very nice unintended behavior when working with notebook-like (markdown/quarto/org) files, where one can just Alt-o and press another keybind that sends the selection to a REPL (currently doing this with wezterm, it can be done with tmux or similar).

[keys.normal]
ret = ":pipe-to cat - <(echo ) | wezterm cli send-text --pane-id `wezterm cli get-pane-direction right`"

Once the issue is fixed, it would be great if there was a textobject to select the injection block at the cursor.