feat(PivotTable): sourceRef

[ShaMan123]

Summary

I want to be able to add pivot tables that source data from a certian range
closes #43

Files changed

lib/doc/pivot-table.js
lib/xlsx/xform/pivot-table/pivot-cache-definition-xform.js
lib/xlsx/xform/pivot-table/pivot-cache-records-xform.js
spec/integration/workbook/pivot-tables-source-ref.spec.js
index.d.ts

Test plan

spec/integration/workbook/pivot-tables-source-ref.spec.js

Related to source code (for typings update)

Checklist

• Only the lines required for the fix/feature are changed (no formatter sweeps, no drive-by refactors)
• Tests use real fixture round-trip (wb.xlsx.load / writeBuffer), not synthetic model objects, where possible
• Checked open PRs (gh pr list --state open) for conflicting changes to the same files
• (If serialization is touched) Output verified to open in Excel, or soffice --headless round-trip clean
• (If --no-verify was used to bypass the pre-commit hook) Reason explained above
• (If a major dep was bumped) Runtime smoke test described above

[ShaMan123]

lint and husky make it quite hard to PR