Added a blank main() in strategy pattern.
Added a blank main() in strategy pattern.

jdavis/rust-design-patterns,ianlet/rust-design-patterns,beni55/rust-design-patterns,beni55/rust-design-patterns,ianlet/rust-design-patterns,jdavis/rust-design-patterns,ianlet/rust-design-patterns,beni55/rust-design-patterns,jdavis/rust-design-patterns,jdavis/rust-design-patterns