[easy28]

Adds JSON Formatter App's browser-based schema tools (data.yaml entry under Development Tools):

• Schema generator: infers a draft 2020-12 schema from a sample document — types, required, array merging, formats, enums
• Schema validator: validates documents with exact error paths

100% client-side (nothing is uploaded; zero network requests after page load). Happy to adjust the entry wording if needed — the README appears to be generated from data.yaml, so this PR only edits that file.

[cla-assistant]

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[cla-assistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

[jviotti]

Please report tools to json-schema.org/tools! We've been trying to push towards actual tools in there instead