Add software development plan elements section

[anmittag]

Added a section outlining software development plan elements.

[github-actions]

Documentation preview for this pull request is available at:
pr-3211: https://eclipse-score.github.io/score/pr-3211/

[anmittag]

changes are visible here https://eclipse-score.github.io/score/pr-3211/platform_management_plan/software_development.html

[PandaeDo]

I would prefer to add the additional coding guidelines to the chapter with the coding guidelines. Same for additional references. I think this would make it more readable than a list at the end of the document with additional information. Appreciate the idea of making it complete!

[anmittag]

@PandaeDo : Adding additional Chapters is fine, but how to ensure all Elements relevant for the Software Development plan is "added". Then I suggest to add the information as you requested AND having a Summary of all relevant SWDevPlan Elements at the end. Agree? Anyhow coding guideleines are already added Line 107ff.

[PandaeDo]

I think that's the main question. It's a responsibility of the maintenance of the plan(s). I think that's an improvement to check against them. So we'll get informed if there are changes. The list will be always updated. Even when you define a document that was defined to realise the plan. So I would agree on update the plan according to additional aspects and add the list at the end.

[anmittag]

part of #3224 => can be closed