add structure to the summary page from announcement page

[avallecam]

Thank you for your comments. I'll reply to them citing each point. When needed, I'll create new issues with the "Reference in new issue" option to solve them isolated.

By @CarmenTamayo:

• Who is the intended audience? The 3 examples of learning personas is okay, but I wouldn't only provide that, I think it's important to first spell out clearly what the pre-requisites and target audience is, and then maybe exemplify this with the learning personas. Otherwise it might be confusing, as most people are not going to be represented by these 3 hypothetical people.

We can adapt the announcement page we prepared for the design of this material (reference).

Add info on:

• What will you learn? but expanded as general learning objectives (as in this reference)
• Who are these lessons for? with the learner personas.
• What is not included in this material? to help the learner decide if this is the correct material to consume or redirect them to others. here we can re-write the related projects section.

Originally posted by @avallecam in #59 (comment)

[avallecam]

Use a callout to emphasise prerequisites and info about the project, as in references:

• https://datacarpentry.org/genomics-r-intro/#prerequisites
• https://datacarpentry.org/r-intro-geospatial/#getting-started

[avallecam]

This section can also introduce a motivational scenario (coming in epiverse-trace/git-rstudio-basics#13)