Subheadline font for inline post content

Contributes to #399 [BUG] Multiple interactions do not collapse into a single notification

Mastodon/In Progress New Layout and Datamodel/InlinePostPreview.swift

@@ -19,6 +19,7 @@ struct InlinePostPreview: View {
             header()
             if let content = viewModel.content {
                 Text(content)
+                    .font(.subheadline)
                     .lineLimit(3)
             }
         }