Tweak code type text

Make the font a little smaller and increase the border of the parent
element.

Fixes gh-40

Author: philwebb

src/main/css/asciidoctor.css

@@ -239,7 +239,7 @@
   box-shadow: inset 0 0 1.75px var(--asciidoctor-pre-border-color);
   display: block;
   overflow-x: auto;
-  padding: 0.75rem;
+  padding: 0.95rem;
   border-radius: 4px;
 }
 
@@ -248,10 +248,10 @@
   text-transform: uppercase;
   display: block;
   position: absolute;
-  top: 0.425rem;
-  right: 0.5rem;
+  top: 0.3rem;
+  right: 0.3rem;
   line-height: 1;
-  font-size: 0.7em;
+  font-size: 0.65em;
   color: var(--asciidoctor-code-data-lang-color);
 }