prevent npm-tests from silently failing by adding cli-flag --unhandled-rejections=strict to npm tests.

[kaizhu256]

this pr fixes following tests from falsely returning exit-code 0 when they fail or crash

npm run test asm
npm run test asm-memory-growth
npm run test wasm

for example

1. ci-logs @ https://github.com/kaizhu256/sql.js/runs/3323383890?check_suite_focus=true clearly show above tests failing, but ci still passes.
2. after applying patch, the ci fails as expected (https://github.com/kaizhu256/sql.js/runs/3323390337?check_suite_focus=true)

this could also be considered a regression of #423 (since nodejs v16+), and reverting that might fix the problem as well.

[lovasoa]

thanks :)