Move vulnerability overrides from npm-format top-level `overrides` to
pnpm-format `pnpm.overrides`. Add flatted override to patch the
high-severity prototype pollution CVE. All 5 high + 3 moderate severity
issues are now resolved.
Remaining: elliptic (low, no patch available upstream).
Co-Authored-By: Paperclip <noreply@paperclip.ing>