Fix indented admonitions

This fixes the formatting for admonitions when they are indented. The
code was missing the indentation for the parts that it was adding, which
made it overall inconsistent and fail to render correctly.

Author: ehuss

mdbook-spec/src/lib.rs

@@ -133,13 +133,15 @@ impl Spec {
                 let lower = caps["admon"].to_lowercase();
                 let term = to_initial_case(&caps["admon"]);
                 let blockquote = &caps["blockquote"];
+                let initial_spaces = blockquote.chars().position(|ch| ch != ' ').unwrap_or(0);
+                let space = &blockquote[..initial_spaces];
                 format!(
-                    "<div class=\"{lower}\">\n\
+                    "{space}<div class=\"{lower}\">\n\
                     \n\
-                    > ***{term}:***\n\
+                    {space}> ***{term}:***\n\
                     {blockquote}\n\
                     \n\
-                    </div>\n",
+                    {space}</div>\n",
                 )
             })
             .to_string()