Platform: styling for <p> and <code> in Emscripten apps.

And docs linking to m.css. Just use that, if you need more.

doc/platforms-html5.dox

@@ -322,6 +322,11 @@ element) from the page to avoid them affecting the canvas. Combining
 @cb{.css} .fullsize @ce with the other @cb{.css} .aspect-* @ce or
 @cb{.css} .width-* @ce classes is not supported.
 
+Besides the canvas, there's minimal styling for @cb{.html} <h1> @ce,
+@cb{.html} <p> @ce and @cb{.html} <code> @ce tags. Putting extra content inside
+the @cb{.css} div#sizer @ce will center it, following the canvas width. If you
+need more advanced styling, check out [m.css](http://mcss.mosra.cz).
+
 @section platforms-html5-events Controlling event behavior
 
 @subsection platforms-html5-events-keyboard Keyboard events

src/Magnum/Platform/WebApplication.css

@@ -35,11 +35,6 @@ body {
   background-color: #2f363f; /*var(--background-color)*/
   color: #dcdcdc; /*var(--color)*/
 }
-h1 {
-  text-align: center;
-  font-size: 1.75rem;
-  font-weight: 600;
-}
 
 /* #container         makes the canvas occupy the whole page width
    #sizer           centers it
@@ -152,4 +147,21 @@ pre#log {
   font-size: 0.8rem; /* so 80 columns fits into 640 pixels */
 }
 
+/* Styling for extra content */
+h1 {
+  text-align: center;
+  font-size: 1.75rem;
+  font-weight: 600;
+}
+#sizer p {
+  text-align: center;
+}
+code {
+  font-family: monospace, monospace, monospace; /* https://en.wikipedia.org/wiki/User:Davidgothberg/Test59 */
+  font-size: 0.9em;
+  padding: 0.125rem;
+  color: #e6e6e6; /*var(--code-color)*/
+  background-color: #282e36; /*var(--code-background-color)*/
+}
+
 /* kate: indent-width 2; */