Improve find-todos

[hjdivad]

Right no w nvim-todos has a binding to search todo comments. I think it's <leader>ft. Add an override for this binding in the relevant lazyvim spec. If we don't already have a spec for this plugin, add it to editor.lua.

The keybinding should use fzf-lua to search todos, but only for lines that appear in the git diff $(git merge-base HEAD origin/master), i.e. those that have been added in local commits.