fix(add): org-id with search option #237

[nobiot]

fix(add): org-id with search option (::*heading) https://github.com/nobiot/org-transclusion/issues/237 c910289

While fixing the issue, I am extending the "add" operation to allow for any link. A lot is still under development and many things will change. But this seems to work without breaking any user-facing commands and function.

Introduced a new function org-transclusion-add-target-marker, which helps transcluding any link (as long as Org can reach the link target and Emacs creates the link's target buffer -- tested with notmuch link successfully).

Refactored the code for the "add" operation with this new approach.