test: add missing ToC entries

These modules were already documented, but not included in the
table of contents.

PR-URL: https://github.com/nodejs/node/pull/27434


Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>