Add events calendar with ICS feed and switch content naming to English

Elternbeirat.Web/Services/PageService.cs

@@ -49,7 +49,7 @@ public sealed class PageService
         var source = File.ReadAllText(path);
 
         var document = Markdown.Parse(source, pipeline);
-        var title = FrontMatter.Read("titel", document, source) ?? slug;
+        var title = FrontMatter.Read("title", document, source) ?? slug;
         var html = Markdown.ToHtml(source, pipeline);
 
         return new Page { Slug = slug, Title = title, ContentHtml = html };