added the Windows impl

Author: its-the-shrimp

library/std/src/sys/os_str/wtf8.rs

@@ -138,6 +138,11 @@ impl Buf {
         self.inner.shrink_to(min_capacity)
     }
 
+    #[inline]
+    pub fn leak<'a>(self) -> &'a mut Slice {
+        Slice::from_inner_mut(self.inner.leak())
+    }
+
     #[inline]
     pub fn into_box(self) -> Box<Slice> {
         unsafe { mem::transmute(self.inner.into_box()) }

library/std/src/sys_common/wtf8.rs

@@ -325,6 +325,11 @@ impl Wtf8Buf {
         self.bytes.shrink_to(min_capacity)
     }
 
+    #[inline]
+    pub fn leak<'a>(self) -> &'a mut Wtf8 {
+        unsafe { Wtf8::from_mut_bytes_unchecked(self.bytes.leak()) }
+    }
+
     /// Returns the number of bytes that this string buffer can hold without reallocating.
     #[inline]
     pub fn capacity(&self) -> usize {