add new types.wit package to hold duration (#98)

Author: bakkot

wit-0.3.0-draft/monotonic-clock.wit

@@ -9,16 +9,14 @@ package wasi:[email protected];
 /// successive reads of the clock will produce non-decreasing values.
 @since(version = 0.3.0-rc-2025-08-15)
 interface monotonic-clock {
+    use types.{duration};
+
     /// An instant in time, in nanoseconds. An instant is relative to an
     /// unspecified initial value, and can only be compared to instances from
     /// the same monotonic-clock.
     @since(version = 0.3.0-rc-2025-08-15)
     type instant = u64;
 
-    /// A duration of time, in nanoseconds.
-    @since(version = 0.3.0-rc-2025-08-15)
-    type duration = u64;
-
     /// Read the current value of the clock.
     ///
     /// The clock is monotonic, therefore calling this function repeatedly will

wit-0.3.0-draft/types.wit

@@ -0,0 +1,8 @@
+package wasi:clocks@0.3.0-rc-2025-08-15;
+/// This interface common types used throughout wasi:clocks.
+@since(version = 0.3.0-rc-2025-08-15)
+interface types {
+    /// A duration of time, in nanoseconds.
+    @since(version = 0.3.0-rc-2025-08-15)
+    type duration = u64;
+}