feat(wpcarro/rust): Include std::fmt::Display example

Gotta know how to `to_string` things

Change-Id: I259ef61ecaf6ae7fabe0b3d211706ba5f429b3a7
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6057
Reviewed-by: wpcarro <wpcarro@gmail.com>
Autosubmit: wpcarro <wpcarro@gmail.com>
Tested-by: BuildkiteCI

users/wpcarro/scratch/rust/src/display/mod.rs

@@ -0,0 +1,13 @@
+use std::fmt;
+
+pub struct Person {
+    pub fname: String,
+    pub lname: String,
+    pub age: i8,
+}
+
+impl fmt::Display for Person {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "{}, {} ({} years old)", self.lname, self.fname, self.age)
+    }
+}