Useful procedural macro crates

As procedural macros can be distributed as crates, a lot of emerging helpful macro crates are available, which can be found at crates.io. Using them can greatly reduce the boilerplate you need to write for generating Rust code. Some of them are as follows:

• derive-new: A derive macro provides a default all-fields constructor for structs and is quite customizable.
• derive-more: A derive macro that circumvents the limitation where we wrap a type for which we already have a lot of traits auto-implemented, but lose the ability to create our own type wrapping for it. This crate helps us provide the same set of traits, even on these wrapper types.
• lazy_static: This crate provides a function-like procedural macro called lazy_static!, where you can declare static values that require dynamically initialized types. For example, you can declare a configuration object as a HashMap and can access it globally across the code base.