Fix missed docs/css folder in tar release #1132

Job	Run time
check-mingw (MINGW64, x86_64, --enable-unicode=yes)	29m 58s
check-msvc (mscng, unicode=yes with-dl=yes)	2m 41s
check-mingw (MINGW64, x86_64, --enable-static --enable-static-linking --enable-unicode=no --enabl...	16m 32s
check-osx	11m 9s
check-msvc (mscng, unicode=no with-dl=no static=yes legacy-crypto=yes ftp=yes)	2m 30s
check-ubuntu-openssl111	2m 19s
check-ubuntu-openssl111 (--enable-static-linking=yes --without-nss --without-gcrypt --without-gnu...	1m 0s
check-msvc (mscrypto, unicode=yes with-dl=yes)	1m 53s
check-ubuntu-openssl300	4m 19s
check-msvc (mscrypto, unicode=no with-dl=no static=yes legacy-crypto=yes ftp=yes)	1m 49s
check-ubuntu-openssl300 (--enable-static --enable-static-linking --without-nss --without-gcrypt -...	1m 11s
check-msvc (openssl-300, unicode=yes with-dl=yes)	10m 29s
check-ubuntu-openssl300 (--enable-static --enable-static-linking --enable-ftp --enable-md5 --enab...	2m 13s
check-msvc (openssl-300, unicode=no with-dl=no static=yes)	11m 18s
check-msvc (openssl-111, unicode=yes with-dl=yes)	2m 58s
check-msvc (openssl-111, unicode=yes with-dl=yes static=yes)	4m 41s
	1h 47m 0s

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