Fix warning: elided lifetime has a name

   --> src\writer.rs:146:73
    |
146 |     pub fn create_element<'a, N>(&'a mut self, name: N) -> ElementWriter<W>
    |                           -- lifetime `'a` declared here                ^ this elided lifetime gets resolved as `'a`
    |
    = note: `#[warn(elided_named_lifetimes)]` on by default

src/writer.rs

@@ -143,7 +143,7 @@ impl<W> Writer<W> {
     /// # }
     /// ```
     #[must_use]
-    pub fn create_element<'a, N>(&'a mut self, name: N) -> ElementWriter<W>
+    pub fn create_element<'a, N>(&'a mut self, name: N) -> ElementWriter<'a, W>
     where
         N: Into<Cow<'a, str>>,
     {