Add first draft of strategie.md

See merge request !77

First draft of Leitungskonferenz.md

See merge request !78

Resolve "Replace linking of PDF files"

Closes #34

See merge request !76

Resolve "Tag blog posts with projects, target groups, and maybe tags"

Closes #31

See merge request !74

Merge branch '31-tag-blog-posts-with-projects-target-groups-and-maybe-tags' of https://edugit.org/Teckids/team-pr/teckids.org into 31-tag-blog-posts-with-projects-target-groups-and-maybe-tags