Add Cargo workspace + common crate with Mode and Method types

common/Cargo.toml

@@ -0,0 +1,13 @@
+[package]
+name = "ubuntu-fido-common"
+version.workspace = true
+edition.workspace = true
+license.workspace = true
+
+[dependencies]
+serde = { workspace = true }
+toml = { workspace = true }
+thiserror = { workspace = true }
+
+[dev-dependencies]
+serde_json = { workspace = true }