Invoke dust to render the stream pages.

At this point the render_blog_stream function is done, but RenderBlogStream::new needs to be implemented to actually generate the render context. The body of this function should be similar to convert_blog_post_page_to_render_context.

src/context/blog_stream.rs

@@ -28,6 +28,8 @@ impl RenderBlogStream {
         output_directory: &Path,
         output_file: &Path,
         original: &[&BlogPost],
+        older_link: Option<String>,
+        newer_link: Option<String>,
     ) -> Result<RenderBlogStream, CustomError> {
         todo!()
     }