Add a prefix to footnote IDs.

This avoids a conflict with multiple blog posts rendering in the same stream.

src/command/build/render.rs

@@ -85,6 +85,7 @@ impl SiteRenderer {
                     config,
                     self.output_directory.as_path(),
                     output_path.as_path(),
+                    None,
                 )?;
                 let render_context = RenderBlogPostPage::new(render_context, &convert_input)?;
                 let rendered_output = renderer_integration.render(render_context)?;
@@ -165,6 +166,7 @@ impl SiteRenderer {
                 config,
                 self.output_directory.as_path(),
                 output_file.as_path(),
+                None,
             )?;
             let blog_stream = RenderBlogStream::new(render_context, &convert_input)?;