Improve speed & keep "lockfileVersion": 2

[JaeseokWoo]

@AndrejGajdos
#24 (comment)
I removed packge-lock.json and kept index.js.

and

Testing & Result

testURL	https://www.google.co.kr/										avg
Improvement	3.375	3.464	3.869	3.575	3.838	3.593	3.928	4.102	3.611	3.356	3.6711
Original	3.717	3.328	4.024	4.997	3.697	3.567	3.743	3.271	3.535	4.182	3.8061
abort script	2.928	2.811	2.784	2.922	2.910	3.783	3.132	4.621	3.253	3.141	3.2285

testURL	https://www.youtube.com/										avg
Improvement	4.199	4.784	4.664	4.088	3.945	4.118	4.177	4.206	4.658	4.037	4.2876
Original	4.130	4.965	4.295	5.154	4.950	5.177	4.101	4.769	4.344	4.217	4.6102
abort script	2.923	2.534	2.528	2.594	2.745	2.475	2.824	2.414	2.861	2.599	2.6497

testURL	https://www.facebook.com/										avg
Improvement	3.188	2.866	2.959	2.911	3.082	2.913	2.944	2.897	3.041	3.038	2.9839
Original	3.005	3.005	3.083	3.094	3.047	3.161	3.050	2.932	3.069	3.045	3.0491
abort script	2.651	2.686	2.959	2.892	2.748	2.958	2.847	3.013	2.807	2.892	2.8453

testURL	https://www.apple.com/kr/										avg
Improvement	2.567	2.585	2.580	2.350	2.459	2.310	2.330	2.682	2.510	3.004	2.5377
Original	2.504	3.091	2.981	3.073	3.316	2.601	3.262	3.815	2.799	2.858	3.03
abort script	1.808	1.641	1.730	1.973	1.843	1.806	1.711	1.778	2.019	1.838	1.8147

Additional considerations

What I have been thinking about for a long time is 'Can I abort script?'
As you can see, a significant performance improvement occurs in test cases with script abort.
However, if metadata is not sufficient and it is a single page application (SPA), I think script is required.

Please check this PR and give me feedback.