Docs and typings fixes for skipUndefined, koa-ts example, and returning options

[kartikdp]

Summary

This PR addresses three open contribution targets with small, low-risk changes:

1. #2149 docs: mark skipUndefined() as deprecated in the query-builder docs.
2. #2361 example: fix examples/koa-ts/api.ts TypeScript errors caused by ctx.request.body being typed as unknown in newer typings.
3. #2309 typings: allow returning(..., options) in Objection typings (for example includeTriggerModifications).

Changes

• Added deprecation note to:
  • doc/api/query-builder/other-methods.md
• Updated koa-ts example to pass typed request bodies to query methods through a small helper:
  • examples/koa-ts/api.ts
• Extended ReturningMethod typings with optional options arg and added typings coverage example:
  • typings/objection/index.d.ts
  • tests/ts/examples.ts

How tested

• npx tsc -p examples/koa-ts/tsconfig.json --skipLibCheck
• npm run test:typings

Notes

If maintainers prefer, I can split this into separate PRs per issue.

If it helps with project maintenance bandwidth, I can also help with ongoing docs/typings/example fixes and issue triage.