End .nojekyll file with newline

Before:

    /path/to$  cat book/.nojekyll
    This file makes sure that Github Pages doesn't process mdBook's output./path/to$  ▎

After:

    /path/to$  cat book/.nojekyll
    This file makes sure that Github Pages doesn't process mdBook's output.
    /path/to$  ▎

Author: dtolnay

src/renderer/html_handlebars/hbs_renderer.rs

@@ -184,7 +184,7 @@ impl HtmlHandlebars {
         write_file(
             destination,
             ".nojekyll",
-            b"This file makes sure that Github Pages doesn't process mdBook's output.",
+            b"This file makes sure that Github Pages doesn't process mdBook's output.\n",
         )?;
 
         write_file(destination, "book.js", &theme.js)?;