Add a crate for experimenting and seeing expanded code

Cargo.toml

@@ -0,0 +1,16 @@
+[package]
+name = "proc-macro-workshop"
+version = "0.0.0"
+edition = "2018"
+publish = false
+
+[[bin]]
+name = "workshop"
+path = "main.rs"
+
+[dependencies]
+bitfield = { path = "bitfield" }
+derive_builder = { path = "builder" }
+derive_debug = { path = "debug" }
+seq = { path = "seq" }
+sorted = { path = "sorted" }

main.rs

@@ -0,0 +1,9 @@
+// Write code here.
+//
+// To see what the code looks like after macro expansion:
+//     $ cargo expand
+//
+// To run the code:
+//     $ cargo run
+
+fn main() {}