Use JSON for map fields

Full Changelog: v0.28.2...v0.29.0

v0.28.2

What's Changed

• Merge from upstream by @simo7 in #1

New Contributors

• @simo7 made their first contribution in #1

Full Changelog: https://github.com/cortea-ai/protobuf-bigquery-go/commits/v0.28.2