Fix the Ampseeker-results book figures

[sanjaynagi]

Closes #48.

In this PR, I have fixed the issue of plots not showing in the results-book! exciting. We use a new env, and add some extras to the _config.yaml

We also:

• Design a new logo based on the old one but a bit sleeker perhaps. A first draft, probably will change in the near future.
• The Ampseeker results book now is built from docs/ into the results/ folder.
• Some minor edits to the PCA nb, labelling axes of variance plot.

[sanjaynagi]

Also closes #50