feat: add a builder() method to HttpsConnector

It's become very idiomatic to have the builder api be accessed this way.

src/connector.rs

@@ -34,6 +34,13 @@ impl<T> HttpsConnector<T> {
     pub fn enforce_https(&mut self) {
         self.force_https = true;
     }
+
+    /// Creates a [`builder::HttpsConnectorBuilder`] to configure a `HttpsConnector`.
+    ///
+    /// This is the same as [`builder::HttpsConnectorBuilder::new()`].
+    pub fn builder() -> builder::ConnectorBuilder<builder::WantsTlsConfig> {
+        builder::ConnectorBuilder::new()
+    }
 }
 
 impl<T> Service<Uri> for HttpsConnector<T>