Add terms to Glossary for block extension examples

[stevepiercy]

This needs to be merged before plone/volto#6560 so that that PR can pull in the Glossary terms.

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📚 Documentation preview 📚: https://plone6--1829.org.readthedocs.build/

[ichim-david]

@stevepiercy I am ok with these additions.
I see that we have this info here:
https://github.com/plone/volto/blob/374dfbcfe6a798fa66f8257e0f560fa1963d2646/docs/source/blocks/extensions.md?plain=1#L12

and
https://github.com/plone/volto/blob/374dfbcfe6a798fa66f8257e0f560fa1963d2646/docs/source/blocks/extensions.md?plain=1#L102

Ppl might not understand what InlineForm is and what it does but it can be a starting point for them to search for what is that component

[stevepiercy]

@ichim-david yup, that's the source of the text I cobbled together.

@erral I simplified it in 05a3bd5.