docs(aio): add short description for entryComponents

[VadimDez]

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[ ] Bugfix
[ ] Feature
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What is the current behavior?

Issue Number: N/A

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Does this PR introduce a breaking change?

[ ] Yes
[x] No

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[VadimDez]

I signed it!

[googlebot]

CLAs look good, thanks!

[trotyl]

Relates to #21257

[gkalpak]

I don't think this description is accurate. They are components that could be created and attached to nodes without being part of another components template (i.e. dynamically), but that doesn't mean they will be compiled/created.

[kapunahelewong]

Thank you, this is great! (PS: you might like to rebase as important changes have been merged. And squash.)

[mlc-mlapis]

@VadimDez ... and also not referenced in any defined routes in that module.

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