fix(redirects): recover legacy URLs Cloudflare leaves un-stripped

[bjohansebas]

close #2407
This is Cloudflare's rule

if:
(ends_with(http.request.uri.path, ".html") and not starts_with(http.request.uri.path, "/2x/") and not http.request.uri.path matches "^/[0-9]{4}/" and not http.request.uri.path eq "/en/changelog/4x.html")
then:
concat("https://expressjs.com/", regex_replace(http.request.uri.path, "\\.html$", "/"))

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