improv(context_drawer): move title out of header row

This moves the title below the header row containing actions and the close button, allowing more room for the title and actions.
Also makes actions an `Element` instead of a `Vec<Element>`, providing more flexibility for developers.

src/widget/context_drawer/mod.rs

@@ -15,9 +15,9 @@ use crate::Element;
 /// An overlayed widget that attaches a toggleable context drawer to the view.
 pub fn context_drawer<'a, Message: Clone + 'static, Content, Drawer>(
     title: Option<Cow<'a, str>>,
-    header_actions: Vec<Element<'a, Message>>,
-    header_opt: Option<Element<'a, Message>>,
-    footer_opt: Option<Element<'a, Message>>,
+    actions: Option<Element<'a, Message>>,
+    header: Option<Element<'a, Message>>,
+    footer: Option<Element<'a, Message>>,
     on_close: Message,
     content: Content,
     drawer: Drawer,
@@ -28,13 +28,6 @@ where
     Drawer: Into<Element<'a, Message>>,
 {
     ContextDrawer::new(
-        title,
-        header_actions,
-        header_opt,
-        footer_opt,
-        content,
-        drawer,
-        on_close,
-        max_width,
+        title, actions, header, footer, content, drawer, on_close, max_width,
     )
 }