Add Result alias (#271)

Adds a `yubikey::Result` alias with `yubikey::Error` as the error type.

Since we only have one `Error` type, this simplifies the return types
where a `Result` is returned.

cli/src/commands/readers.rs

@@ -53,7 +53,7 @@ impl ReadersCmd {
         index: usize,
         name: &str,
         serial: Serial,
-    ) -> Result<(), io::Error> {
+    ) -> io::Result<()> {
         stream.set_color(ColorSpec::new().set_bold(true))?;
         write!(stream, "{:>3}:", index)?;
         stream.reset()?;

cli/src/commands/status.rs

@@ -51,7 +51,7 @@ impl StatusCmd {
         stream: &mut StandardStreamLock<'_>,
         name: &str,
         value: impl ToString,
-    ) -> Result<(), io::Error> {
+    ) -> io::Result<()> {
         stream.set_color(ColorSpec::new().set_bold(true))?;
         write!(stream, "{:>12}:", name)?;
         stream.reset()?;