Add “Recycling” entry

Commonly used in VanillaJS and by libraries such as [Inferno](https://github.com/trueadm/inferno): it's the process or re-using JavaScript objects/DOM nodes that been pooled after use, rather than creating new objects/DOM nodes each again.

Start by locating the existing glossary entries and their formatting in the SJSJ repository. Add a “Recycling” entry using the supplied definition and links, then verify that it matches the surrounding documentation style.

Written by the indexing model from the issue text.