Update glossary items

[maneesha]

We now have a single glossary page: https://carpentries-beta-handbook-preview.netlify.app/pages/glossary.html

Most of the items are missing definitions, so definitions need to be added in. Definitions can be added by replacing the text "definition goes here" with the intended definition. Be sure the definition text is indented.

We also need to identify cross-referenced items (currently noted as "See also..."). @brynnelliott has identified this as ableist language. We should decide what language we want to use instead of that before creating all these cross-referenced links, so we don't have to update them all later.

[maneesha]

@OscarSiba Had you decided whether to keep the glossary in the handbook or in the existing glossary (https://github.com/carpentries/community-engagement/blob/main/glossary.md)?

As we have a lot to do, it may be easier to keep the existing glossary as it is, and consider moving it to the handbook later.