docs(headless): typedoc beta note for ssr-commerce

[jpmarceau]

https://coveord.atlassian.net/browse/DOC-16522

I only noticed yesterday that we have public reference documentation for the ssr-commerce package under headless (the one in headless-react is already covered). It's in open beta, so I add a string to that effect in the relevant titles.

E.g.:

[github-actions]

Pull Request Report

PR Title

✅ Title follows the conventional commit spec.

Live demo links

• Storybook

• Playwright report

Bundle Size

File	Old (kb)	New (kb)	Change (%)
case-assist	244.2	244.2	0
commerce	355.5	355.5	0
search	415.5	415.5	0
insight	406.7	406.7	0
recommendation	256.3	256.3	0
ssr	409.3	409.3	0
ssr-commerce	373.2	373.2	0

SSR Progress

Use case	SSR (#)	CSR (#)	Progress (%)
search	39	44	89
recommendation	0	4	0
case-assist	0	6	0
insight	0	27	0
commerce	0	15	0

Detailed logs

search : buildInteractiveResult
search : buildInteractiveInstantResult
search : buildInteractiveRecentResult
search : buildInteractiveCitation
search : buildGeneratedAnswer
recommendation : missing SSR support
case-assist : missing SSR support
insight : missing SSR support
commerce : missing SSR support