feat(http2): configure HTTP/2 frame size in the high-level builders too (#2214)

Oops, I missed this in #2211.

src/server/mod.rs

@@ -342,6 +342,16 @@ impl<I, E> Builder<I, E> {
         self
     }
 
+    /// Sets the maximum frame size to use for HTTP2.
+    ///
+    /// Passing `None` will do nothing.
+    ///
+    /// If not set, hyper will use a default.
+    pub fn http2_max_frame_size(mut self, sz: impl Into<Option<u32>>) -> Self {
+        self.protocol.http2_max_frame_size(sz);
+        self
+    }
+
     /// Sets the [`SETTINGS_MAX_CONCURRENT_STREAMS`][spec] option for HTTP2
     /// connections.
     ///