Add version.json to match go-multibase

[acul71]

Summary

• Fixes Add version.json to match go-multibase #46
• Adds root version.json with "version": "v2.0.0" for ecosystem tooling parity with go-multibase
• Wires the file into bump-my-version so the v-prefixed value stays in sync on release

Demo / evidence

$ cat version.json
{
  "version": "v2.0.0"
}

$ bump-my-version bump patch --dry-run --allow-dirty
# shows version.json would change v2.0.0 → v2.0.1
# and would add version.json to the release commit

Explanation: Python package metadata keeps bare 2.0.0; only version.json stores the go-style v prefix. The dry-run confirms bumpversion updates that file correctly.

Test plan

• make lint
• make typecheck
• make test
• make docs-ci
• bump-my-version bump patch --dry-run --allow-dirty includes version.json

Made with Cursor

[acul71]

Demo logs (bump dry-run)

$ cat version.json
{
  \"version\": \"v2.0.0\"
}

$ bump-my-version bump patch --dry-run --allow-dirty

This shows version.json is included in the bump set and would move v2.0.0 → v2.0.1 alongside the other version files.

[acul71]

@sumanjeet0012 Could you please review this PR when you have a chance? Thanks!