Bug: absURL to relURL

[pacollins]

Description

Change all absURL to relURL, and all non-essential .site.baseURL to "/" | relURL.

Motivation and Context

Fixes #80

How Has This Been Tested?

Hugo Version: v0.30

Browser(s): Chrome

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation, including theme.toml, accordingly.
• I have read the Contributing Document.