feat: update wording including "micro-backend"

[SebConejo]

Description

I replaced the "heading-cms" concept by "micro-backend" one.

Check the NPM packages that require a new publication or release:

• manifest
• add-manifest
• @mnfst/sdk

Check list before submitting

• I have performed a self-review of my code (no debugs, no commented code, good naming, etc.)
• I wrote the relative tests
• I created a PR for the documentation if necessary and attached the link to this PR
• I updated the "examples" dependencies if new packages have been released
• This PR is wrote in a clear language and correctly labeled

[vercel]

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Name	Status	Preview	Comments	Updated (UTC)
manifest-schema	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Dec 18, 2024 4:37pm

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