librustdoc: impl core::fmt::Write for rustdoc::html::render::Buffer

Signed-off-by: Muhammad Falak R Wani <falakreyaz@gmail.com>

src/librustdoc/html/format.rs

@@ -64,6 +64,12 @@ crate struct Buffer {
     buffer: String,
 }
 
+impl core::fmt::Write for Buffer {
+    fn write_str(&mut self, s: &str) -> fmt::Result {
+        self.buffer.write_str(s)
+    }
+}
+
 impl Buffer {
     crate fn empty_from(v: &Buffer) -> Buffer {
         Buffer { for_html: v.for_html, buffer: String::new() }