Add support for org-mode format

[EncodePanda]

Org mode for Emacs is a highly flexible structured plain text file format used in Emacs.

In essence, it will be similar to what markdown produces. Should be an easy feature to add.

Markdown produces:

[Nix manual](https://nixos.org/manual/nix/stable/#chap-introduction)

org-mode should produce:

[[https://nixos.org/manual/nix/stable/][Nix Manual]]

[malcook]

This can be accomplished by configuration with no code change.

org mode links can be created by defining the following custom link format in the extensions options dialog:

Name	Format	Filter
orgmode	[[%url%][%text%]]