Highlight the whole line when too many individual words changed

[Urgau]

This PR update our words highlighting logic to highlight the whole line when more than 60% of the individual words changed.

Currently	This PR

Testing:

• https://triagebot.infra.rust-lang.org/gh-range-diff/rust-lang/rust/d1961bebe091816d8ce9771f29ad471dda398f5d..730f7b808d09dbdffe64fac82935e8bf007e3a3a/eab3d9776409dfb564130c3cd5f6ecacef3d3279..02e8e3ed2d03576a26a9b30d46168de2abadf910
• http://localhost:8000/gh-range-diff/rust-lang/rust/d1961bebe091816d8ce9771f29ad471dda398f5d..730f7b808d09dbdffe64fac82935e8bf007e3a3a/eab3d9776409dfb564130c3cd5f6ecacef3d3279..02e8e3ed2d03576a26a9b30d46168de2abadf910

[Kobzol]

It would be a bit more prcise if consecutive highlighted boxes were merged together, rather than highlighting the whole line based on the heuristic, but that sounds painful to implement, and the new version looks IMO better than the old one, so 👍

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