Current CI/CD Security Guide UI/UX Improvement with a Stepper

I suggest we use a stepper component similar to Material UI's [Stepper](https://mui.com/material-ui/react-stepper/) to help with the [CI/CD Security Guide](https://cicd-cybersecurity.netlify.app/cicd-security-guide/) navigation. Currently it is not clear where the user is at in terms of navigation in relation to the different phases and the steps. An example of such a stepper component would look like the below:

Currently we only have breadcrumbs, and it is not very visually effectively as a sign post.

Open the CI/CD Security Guide and compare its current breadcrumb navigation with the proposed Material UI Stepper example. Trace the guide's phases and steps, then make the current phase and step visibly clear; done when navigation provides an effective signpost throughout the guide.

Written by the indexing model from the issue text.