[extractor/generic] Improve squarespace detection and fix test (closes #21859, refs #21294, refs #21802)
[extractor/generic] Improve squarespace detection and fix test (closes #21859, refs #21294, refs #21802)

nyuszika7h/youtube-dl,hakatashi/youtube-dl,Orochimarufan/youtube-dl,ozburo/youtube-dl,ozburo/youtube-dl,yan12125/youtube-dl,Tatsh/youtube-dl,rg3/youtube-dl,nyuszika7h/youtube-dl,Orochimarufan/youtube-dl,rg3/youtube-dl,vinegret/youtube-dl,Tatsh/youtube-dl,hakatashi/youtube-dl,yan12125/youtube-dl,spvkgn/youtube-dl,vinegret/youtube-dl,erikdejonge/youtube-dl,erikdejonge/youtube-dl,remitamine/youtube-dl,remitamine/youtube-dl,spvkgn/youtube-dl