doc: add introduced_in metadata to _toc.md

Allow users to switch to the table of contents for older versions of Node.js. This gets rid of the "Failed to add alternative version link" warnings when building docs. PR-URL: #19113 Reviewed-By: Luigi Pinca <[email protected]> Reviewed-By: Benjamin Gruenbaum <[email protected]> Reviewed-By: Colin Ihrig <[email protected]> Reviewed-By: Gibson Fahnestock <[email protected]> Reviewed-By: Matheus Marchini <[email protected]> Reviewed-By: James M Snell <[email protected]> Reviewed-By: Jon Moss <[email protected]> Reviewed-By: Sakthipriyan Vairamani <[email protected]>

Author: Trott

doc/api/_toc.md

@@ -1,5 +1,9 @@
 @// NB(chrisdickinson): if you move this file, be sure to update tools/doc/html.js to
 @// point at the new location.
+@// tools/doc/html.js to point at the new location.
+
+<!--introduced_in=v0.10.0-->
+
 *[About these Docs](documentation.html)
 *[Usage & Example](synopsis.html)