Improve Swift in VSCode getting started article

[alexandersandberg]

Motivation:

Fixes #704.

Modifications:

• Adds @matthewbastien and @plemarquand to the list of authors (please let me know if I want to add a description to your profiles as well!)
• Changed 2 links from absolute to relative (when on Swift.org, it's better to use relative links as they also will work in other environments, e.g. when running the website locally)

Result:

[alexandersandberg]

@swift-ci please test