Add an example using strum

Cargo.toml

@@ -35,3 +35,4 @@ paw_dep = { version = "1", optional = true, package = "paw" }
 [dev-dependencies]
 trybuild = { version = "1.0.5", features = ["diff"] }
 rustversion = "1"
+strum = { version = "0.20", features = ["derive"] }

examples/enum_in_args_with_strum.rs

@@ -0,0 +1,27 @@
+use structopt::StructOpt;
+use strum::{EnumString, EnumVariantNames, VariantNames};
+
+const DEFAULT: &str = "txt";
+
+#[derive(StructOpt, Debug)]
+struct Opt {
+    #[structopt(
+        long,
+        possible_values = Format::VARIANTS,
+        case_insensitive = true,
+        default_value = DEFAULT,
+    )]
+    format: Format,
+}
+
+#[derive(EnumString, EnumVariantNames, Debug)]
+#[strum(serialize_all = "kebab_case")]
+enum Format {
+    Txt,
+    Md,
+    Html,
+}
+
+fn main() {
+    println!("{:?}", Opt::from_args());
+}