manual: Document org-babel-tangle-finished-hook

* etc/ORG-NEWS: Mention new hook, `org-babel-tangle-finished-hook'.

* doc/org-manual.org (Tangle hooks): Mention new hook,
`org-babel-tangle-finished-hook'.

doc/org-manual.org

@@ -18610,6 +18610,10 @@ expanded anyway.
   ~org-babel-tangle~, making it suitable for post-processing,
   compilation, and evaluation of code in the tangled files.
 
+- ~org-babel-tangle-finished-hook~ ::
+  #+vindex: org-babel-tangle-finished-hook
+  This hook is run after post-tangle hooks, in the original buffer.
+
 *** Jumping between code and Org
 :PROPERTIES:
 :UNNUMBERED: notoc

etc/ORG-NEWS

@@ -301,6 +301,13 @@ to pass the contents of a named code block as a string argument.
 The new property =ORG-IMAGE-ACTUAL-WIDTH= can override the global
 variable ~org-image-actual-width~ value for inline images display width.
 
+*** New ~org-babel-tangle-finished-hook~ hook run at the very end of ~org-babel-tangle~
+
+This provides a proper counterpart to ~org-babel-pre-tangle-hook~, as
+~org-babel-post-tangle-hook~ is run
+per-tangle-destination. ~org-babel-tangle-finished-hook~ is just run
+once after the post tangle hooks.
+
 ** New options
 *** New custom settings =org-icalendar-scheduled-summary-prefix= and =org-icalendar-deadline-summary-prefix=