Merge branch 'lambda' into 'main'

book/src/part08.md

codes/rust_lang/part08/src/big_int.rs

codes/rust_lang/part08/src/binary_operator.rs

codes/rust_lang/part08/src/custom_int.rs

codes/rust_lang/part08/src/find.rs

codes/rust_lang/part08/src/io.rs

codes/rust_lang/part08/src/lib.rs

codes/rust_lang/part08/src/main.rs

codes/rust_lang/part08/src/minimum.rs

codes/rust_lang/part08/src/something_or_nothing.rs

slides/src/SUMMARY.md

slides/src/closures.md