[src/doc/manifest] Add section on Migrating to `gitignore`-like pattern matching
[src/doc/manifest] Add section on Migrating to `gitignore`-like pattern matching

Tracking issue: https://github.com/rust-lang/cargo/issues/4268

nipunn1313/cargo,tsurai/cargo,rustyhorde/cargo,tshepang/cargo,tshepang/cargo,nipunn1313/cargo,rust-lang/cargo,eminence/cargo,rustyhorde/cargo,vojtechkral/cargo,eminence/cargo,achanda/cargo,achanda/cargo,vojtechkral/cargo,rust-lang/cargo,rustyhorde/cargo,eminence/cargo,tsurai/cargo,rust-lang/cargo,eminence/cargo,tsurai/cargo,tshepang/cargo,tsurai/cargo,achanda/cargo,nipunn1313/cargo,tshepang/cargo,rustyhorde/cargo,vojtechkral/cargo,vojtechkral/cargo,rust-lang/cargo,achanda/cargo,nipunn1313/cargo,tsurai/cargo