Add support for Mailplane links to org-mode

mailplane.el

    ;; attempt to add mailplane support
    (defcustom org-mailplane-url-protocol "mailplane"
      "Protocol identifier for Mailplane links."
      :group 'org-mailplane
      :type 'string)

    (defun org-mailplane-follow (email-id)
      "Open mailplane with given EMAIL-ID."
      (browse-url (concat "mailplane:" email-id)))

    (org-link-set-parameters org-mailplane-url-protocol :follow #'org-mailplane-follow)

Without it, was getting "No match - create as a new heading" popup when trying to click on mailplane links in org. Just stick this piece somewhere inside (with-eval-after-load 'org ...).