ci: add Dependabot config for bundler and GitHub Actions - #202

Changed pages include:

• index.html - view
• 2017-phd-workshops-on-computational-methods/index.html - view
• 404.html - view
• about-python-lectures/index.html - view
• about/index.html - view
• acknowledging/index.html - view
• analytics-dashboard/index.html - view
• bayesian-workshop-2017/index.html - view
• books/index.html - view
• chicago-fed-workshop/index.html - view

There are more changes not included in the list