Use GitHub Flavored Markdown alerts for some notes

[HonkingGoose]

Changes:

• Use GitHub Flavored Markdown alerts for some notes

Context:

We can make the Note parts "pop" a bit more, by using the GitHub Flavored Markdown alert syntax.

The GitHub Docs, Basic writing and formatting syntax, alerts also shows the alert types:

• Note
• Tip
• Important
• Warning
• Caution

I'm doing a one to one replacement for now. The GitHub docs warn us that:

Use alerts only when they are crucial for user success and limit them to one or two per article to prevent overloading the reader. Additionally, you should avoid placing alerts consecutively. Alerts cannot be nested within other elements.

So I'm keeping the nested notes in the old style, as nesting is forbidden. 😄