doc,src,lib: clarify experimental status of Web Storage support #946

Job	Run time
Build slim tarball	1m 33s
aarch64-darwin: with shared libraries	2h 1m 11s
x86_64-linux: with shared libraries	2h 28m 27s
x86_64-darwin: with shared libraries	4h 58m 40s
aarch64-linux: with shared libraries	2h 17m 19s
	11h 47m 10s

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