Rewrite: uncoupling STU3 and R4 and removed request for feedback

[HarmkeKoning]

Closes#91 and closes#58.

A draft for our homepage and data exchange page.
Can you take a look at the texts and the position of the warning box?

[ArdonToonstra]

The warning box is now falling away at the bottom I would say. Perhaps its better right behind the first section after line 7?

Perhaps instead of a html div with warning we could try one of the below markdown options. Maybe the Note. Not sure if they are supported in the IG publisher though.

Note

Highlights information that users should take into account, even when skimming.

Tip

Optional information to help a user be more successful.

Important

Crucial information necessary for users to succeed.

Warning

Critical content demanding immediate user attention due to potential risks.

Caution

Negative potential consequences of an action.

[HarmkeKoning]

The IG publisher doesn't support the markdown options. But i found these options specifically for the IG publisher:
Styles
There are defined styles for narrative:

stu-note - used to note important changes, questions, or open issues of relevance to implementers
dragon - used to warn about specific risks or cautions implementers should be aware of
note-to-balloters - used to note changes, questions, or other areas of specific interest to balloters
modified-content - a part of the specification that has changed since the last official release
new-content - a part of the specification that is new since the last official release
feedback - information about how to provide feedback about a specification. (Not usually used in HL7-international published specs.)

At: https://build.fhir.org/ig/FHIR/ig-guidance/best-practice.html

Maybe one of those fits this purpopse?

[ArdonToonstra]

Mmm, they don't exactly match... What if we just describe this in a section? A 1.3 section? Without the warning banner.

[ArdonToonstra]

See comment inline on the location of the note to users about STU3 IG.