Decrease left margins on blockquotes to 1em.

It is intentionally impossible to add borders to blockquotes via CSS:
<https://bugreports.qt.io/browse/QTBUG-23244>.

Bug: https://github.com/Nheko-Reborn/nheko/issues/704

resources/qml/delegates/TextMessage.qml

@@ -29,6 +29,7 @@ MatrixText {
         border-collapse: collapse;
         border: 1px solid " + Nheko.colors.text + ";
     }
+    blockquote { margin-left: 1em; }
     </style>
     " + formatted.replace("<pre>", "<pre style='white-space: pre-wrap; background-color: " + Nheko.colors.alternateBase + "'>").replace("<del>", "<s>").replace("</del>", "</s>").replace("<strike>", "<s>").replace("</strike>", "</s>")
     width: parent ? parent.width : undefined