docs: add a FAQ entry about git-deps and relative file paths #1208

Job	Run time
examples-darwin	3m 32s
check-dead-code	24s
check-fmt	40s
examples-linux (alt-registry)	1m 27s
examples-linux (build-std)	1m 29s
tests (https://releases.nixos.org/nix/nix-2.18.2/install)	2m 27s
examples-linux (cross-musl)	1m 26s
tests (https://releases.nixos.org/nix/nix-2.18.2/install, --override-input nixpkgs $(./ci/ref-fro...	2m 26s
examples-linux (cross-rust-overlay)	1m 29s
examples-linux (cross-windows)	1m 26s
examples-linux (custom-toolchain)	1m 26s
examples-linux (end-to-end-testing)	1m 30s
examples-linux (quick-start)	1m 27s
examples-linux (quick-start-simple)	1m 31s
examples-linux (quick-start-workspace)	1m 35s
examples-linux (sqlx)	1m 24s
examples-linux (trunk-workspace)	1m 36s
examples-linux (trunk)	1m 34s
all systems go	0s
	28m 49s

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