Update HTML format (reverse pre and code tags)

[pawamoy]

Type of changes

• Bug fix [BUG] export_html leaks style into the page #2641
• New feature
• Documentation / docstrings
• Tests
• Other

Checklist

• I've run the latest black with default args on new code.
• I've updated CHANGELOG.md and CONTRIBUTORS.md where appropriate.
• I've added tests for new code.
• I accept that @willmcgugan may be pedantic in the code review. 😂

Description

I've reversed the pre and code tags in the base HTML format. Otherwise it looks like the browser terminates the first code tag early, wraps it in a p, and then re-uses code in the pre tag 😕

PRE:

The PRE element tells visual user agents that the enclosed text is "preformatted". When handling preformatted text, visual user agents:

May leave white space intact.
May render text with a fixed-pitch font.
May disable automatic word wrap.
Must not disable bidirectional processing.

CODE:

Designates a fragment of computer code.

[pawamoy]

Let me know if you want me to update the changelog.

[pawamoy]

OK I'll clone that locally and fix the tests.