templates/portfolio.html: Fix closing H5 tag
templates/portfolio.html: Link NetControl project to its page at GitHub
portfolio: Add description from course "Intro to AI"

The template from `project-sample.html` has been taken as an example for
now, but it will need changing so that it displays info about the course,
such as contents, university, statement of accomplishment, etc.
templates/portfolio.html: Add image to NetControl