doc,src,lib: clarify experimental status of Web Storage support #864

Job	Run time
Build slim tarball	1m 33s
x86_64-linux: with shared libraries	50m 26s
aarch64-linux: with shared libraries	43m 8s
x86_64-darwin: with shared libraries	2h 4m 52s
aarch64-darwin: with shared libraries	32m 9s
	4h 12m 8s

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