normalize_path: Add `Append` mode #1140

Job	Run time
cargo-hack	1m 13s
check-docs	43s
check	44s
cargo-public-api-crates	15s
cargo-deny check (advisories)	19s
cargo-deny check (bans licenses sources)	49s
test-versions (stable)	1m 23s
style	14s
test-versions (beta)	1m 24s
test-msrv	2m 35s
test-versions (nightly)	1m 13s
	10m 52s

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