feat(input): implement parsing from ws-separated string

Signed-off-by: Matej Focko <mfocko@redhat.com>

src/input.rs

@@ -63,3 +63,15 @@ where
         .map(str::to_string)
         .collect()
 }
+
+/// Parses a string of whitespace separated elements and returns them as
+/// a collection.
+pub fn parse_ws_separated<B, T: FromStr>(s: &str) -> B
+where
+    B: FromIterator<T>,
+    <T as FromStr>::Err: Debug,
+{
+    s.split_ascii_whitespace()
+        .map(|n| n.parse().unwrap())
+        .collect()
+}