Add section on ensuring reproducibility

[sjspielman]

This issue tracks adding a new navbar section called Ensuring reproducibility where we will introduce the different strategies used in OpenScPCA that ensure project reproducibility over time. This should have the following overall structure:

• index.md will contain the figure being made in #491, and will briefly explain the role of each component in that figure in OpenScPCA
• software-environments/: This is where the rearranged software docs will live (#458)
• docker/: Current docker docs will be moved here (#492), and more docs will be added as well.
• analysis-module-workflows/: document GHAs in OpenScPCA-analysis
• openscpca-nf/: document OpenScPCA-nf

[sjspielman]

Aside from openscpca-nf, all sections here have been added. Adding that section is separately tracked by #519, so this issue can be closed.