fix: ship LICENSE, NOTICE and README in the published packages

[justFU7]

Description

The published packages of this monorepo are missing their legal files, and two of the three are missing
their README as well.

Each manifest asks for them:

"files": ["/esm", "/cjs", "/browser", "LICENSE", "README.md"]

but those paths resolve relative to packages/<pkg>/, and LICENSE, NOTICE and (for two of the three
packages) README.md exist only at the repository root, so npm has nothing to match and packs neither.

Evidence from the published artifacts

Listing the current tarballs, everything outside esm/, cjs/ and browser/:

package	version	files at the tarball root
@asyncapi/parser	3.6.3	package.json
@asyncapi/multi-parser	2.4.0	package.json
@asyncapi/openapi-schema-parser	3.1.0	package.json, README.md

$ curl -sLO https://registry.npmjs.org/@asyncapi/parser/-/parser-3.6.3.tgz
$ tar tzf parser-3.6.3.tgz | grep -vE "^package/(esm|cjs|browser)/"
package/package.json

So no package ships a LICENSE or a NOTICE, and only openapi-schema-parser ships a README.

Why it matters

Apache-2.0 section 4(a) requires a copy of the licence to accompany each distribution of the work, and 4(d)
requires the NOTICE attributions to travel with it. The npm tarball is how essentially every consumer
receives these packages, and it currently carries neither. Separately, @asyncapi/parser and
@asyncapi/multi-parser render with no README on npmjs.com.

Changes

• new scripts/copy-legal.js, copying the root LICENSE and NOTICE into the package being published, plus
  the root README.md only when the package does not ship one of its own (so
  openapi-schema-parser’s README is left alone);
• each package runs it from prepublishOnly, so the files exist by the time npm packs;
• NOTICE added to each files array next to the LICENSE entry that was already there;
• the copied files are gitignored per package.

No new dependency - prepublishOnly already existed in all three manifests, this only prepends one step.

Verifying

npm -w @asyncapi/parser run copy:legal && npm pack -w @asyncapi/parser --dry-run

LICENSE, NOTICE and README.md now appear in the pack listing.

[changeset-bot]

🦋 Changeset detected

Latest commit: afdb541

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 3 packages

Name	Type
@asyncapi/parser	Patch
@asyncapi/multi-parser	Patch
@asyncapi/openapi-schema-parser	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

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[sonarqubecloud]

Quality Gate passed

Issues
2 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud