Support for --multiline

[wpcarro]

Does deadgrep support the multiline option? If not, any ideas for a workaround?

Something like this might be nice:

(defcustom deadgrep-additional-flags
  '("--multiline")
  "List of additional arguments that will be passed to rg.")

(add-to-list deadgrep-additional-flags "--another-flag")

[wpcarro]

Support something like deadgrep-additional-flags might also help support ideas like #24