Use sentence case for setup guides

[pkeilbach]

While writing CONTRIBUTING.md, I noticed that it is more appropriate to use sentence case for the headlines.

The scope of this issue is to update all technical documentation to use sentence case in their headlines, namely:

• docs/getting_started.md
• docs/assignments.md
• docs/presentations.md
• docs/course_profile.md

Also ensure that with sentence case, the headlines are more descriptive where it makes sense, e.g. here: ## Starting the Jupyter server instead of ## Jupyter

(Note that Jupyter is still capitalized in sentence case because it is a proper noun)

[browo097302]

Hi, I'm happy to help with this, could I be assigned for this issue?

[pkeilbach]

Awesome, @browo097302 , I will assign you to the issue!

Maybe you can wait a bit with the implementation until I finish the preparations for the semester 👉🏼 #134

Also to be fair with the other students before we kick off the semester officially. ✌🏼

[browo097302]

Great, thanks will do