[arclint] Ignore spelling for generated package-lock.json files

Summary:
Coincidental lint warnings are occasionally thrown on these generated files (e.g. in D11120). This diff ignores package-lock.json files when running the spelling linter.

These files are generated, but cannot have comments in them, so can't just mark them as generated to otherwise ignore.

Test Plan: arc lint and ensure package-lock.json files are not scanned. One way to do it is to arc patch 11120, arc lint, observe errors, make this change, arc lint again, observe no errors.

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Differential Revision: https://reviews.bitcoinabc.org/D11129