doc: Update docstrings of `buffer_append_str` and `get_container_info` #209

Job	Run time
Vendored archive	2m 5s
Create binary (x86_64-unknown-linux-gnu, --features full --features openssl-vendored, debian:book...	6m 16s
Create binary (x86_64-unknown-linux-musl, --no-default-features --features full --features all-ve...	6m 25s
Create binary (aarch64-unknown-linux-gnu, --features full --features openssl-vendored, debian:boo...	7m 42s
Create binary (aarch64-unknown-linux-musl, --no-default-features --features full --features all-v...	6m 46s
Create binary (riscv64gc-unknown-linux-gnu, --features full --features openssl-vendored, debian:s...	7m 25s
Push docker multi-arch image	1m 18s
Create release	23s
	38m 20s

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