Org-id: Clarify customization documentation for org-id, ts option

* lisp/org-id.el (org-id-ts-format, org-id-method): Clarify docstrings.
* doc/org-manual.org (Handling Links): Mention org-id-method in
the manual.

Release Org 9.4

Adding release tag

Org-Mode 9.3.7

Org-Mode 9.3.6

Org-Mode 9.3.5

Org-Mode 9.3.4

Org-Mode 9.3.3

Org-Mode 9.3.2

Org-Mode 9.3.1