docs($sce): fix code samples and example

The code samples were using `<pre>` tags rather than code fences (```) so they were
not being displayed correctly.

The inline code example (defined by a `<example>` element) had been placed in an
`@example` jsdoc tag, so rather than appearing inline at the declaration point in
the text, they were being appended to the end of the document in the `Example` section.

Closes #8053