Improve Any derive documentation #968

Job	Run time
runefmt	1m 38s
rustfmt	5s
clippy	1m 56s
docs	1m 58s
basics	1s
miri_rune_alloc	5m 18s
no_default_features	51s
miri_rune	6m 47s
build_feature (capture-io)	43s
msrv	1m 58s
build_feature (cli,doc)	1m 17s
no_std_minimal	2m 38s
build_feature (cli,fmt)	1m 23s
wasm	1m 1s
build_feature (cli)	1m 26s
build_feature (workspace)	48s
build_feature (languageserver)	1m 9s
build_feature (byte-code)	43s
test	10m 28s
	42m 8s

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