Add support for transcripts schema version 2.2

[skydudie]

This pull request introduces support for version 2.2 of the transcripts schema, including updated example documents and changelog documentation. The changes add new features to the schema, such as an optional network field for blockchain certificate issuance, and provide comprehensive example JSON files to illustrate usage.

Schema versioning and support:

• Added support for transcripts schema version 2.2 in both the schema publishing script (publishSchema.sh) and the main schema loader (src/index.js), ensuring the new schema version is available for use. [1] [2]

Schema enhancements:

• Documented the addition of a new optional network field (with chain and chainId properties) for DNS-TXT Blockchain issued certificates, aligning with OpenAttestation standards. (https://github.com/Open-Attestation/open-attestation/blob/f1339e9af90369ca621aaf1cc246bfcada7264ea/src/2.0/schema/schema.json#L224)

Example documents:

• Added three comprehensive example JSON documents for schema version 2.2:
  • example.json: Demonstrates a transcript with the new network field and various recipient, issuer, qualification, and skills data.
  • example-did-document.json: Shows a transcript with multiple issuers using DID and DNS-TXT identity proofs.
  • example-dns-did-document.json: Provides an example featuring DNS-DID identity proof and additional issuer/recipient details.

[Isaac-kps]

LGTM