contact: Increase input field width & height

contact: Remove (comment) 'Contact Us' paragraph content.

* style.css: Rename blue_button to blue-button, change from ID
selector to class && relocate rounded-border styling to rounded-border
class selector.
Fix outline headers && footer styling issues

* Ensure that all outline header tags (h1..h6) consistently use
Lora font.

* Fix footer padding & width.
Introduce breadcrumbs for practice page

* Introduce Markdown-filtered topic pages for practice page.
* Move practice route into its own file; routes/practice.js.
* New color scheme (WIP).
Split contact routing into its own file; routes/contact.js