feat(fs): add copy

src/fs/file.rs

@@ -41,4 +41,25 @@ impl<'base, 'path> PathReal<'base, 'path, FileMarker> {
         self.check_error()?;
         std::fs::write(self.as_pathbuf(), contents).map_err(Error::Io)
     }
+
+    /// Copies the contents of a file to another file.
+    ///
+    /// Wrapper for [std::fs::copy]
+    ///
+    /// ```
+    /// # fn try_main() -> kxio::fs::Result<()> {
+    /// let fs = kxio::fs::temp()?;
+    /// let src_path = fs.base().join("foo");
+    /// let dest_path = fs.base().join("bar");
+    /// let src = fs.file(&src_path);
+    /// # fs.file(&dest_path).write("new file contents")?;
+    /// let dest = fs.file(&dest_path);
+    /// src.copy(&dest)?;
+    /// # Ok(())
+    /// # }
+    /// ```
+    pub fn copy(&self, dest: &PathReal<'base, 'path, FileMarker>) -> Result<u64> {
+        self.check_error()?;
+        std::fs::copy(self.as_pathbuf(), dest.as_pathbuf()).map_err(Error::Io)
+    }
 }