set content type in graphql request

js/customElements/blogFooter.js

js/customElements/blogIndex.js

js/customElements/commentsDisplay.js

js/customElements/contactMailButton.js

js/customElements/ebkBanner.js

js/customElements/newComment.js

js/customElements/sellingTable.js

js/customElements/skills.js

js/viewPost.js

public/API/graphql.php

public/impressum.html