chore: release v1.3.0

[piecioshka]

Release after the TypeScript migration (adds type declarations + compiled dist, non-breaking → minor). Adds prepublishOnly build safeguard.

[Copilot]

Pull request overview

This PR prepares the encoding-checker package for the v1.3.0 release by bumping package versions and adding an npm publish-time build safeguard, consistent with a post–TypeScript-migration release that ships dist/ and types/.

Changes:

• Bump package version from 1.2.0 → 1.3.0 in package.json and package-lock.json.
• Add prepublishOnly script to ensure npm run build runs before publishing.

Reviewed changes

Copilot reviewed 1 out of 2 changed files in this pull request and generated no comments.

File	Description
package.json	Bumps version to 1.3.0 and adds prepublishOnly build safeguard.
package-lock.json	Updates lockfile package version metadata to 1.3.0.

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