refactor: 重构markdown

Yi.BBS.Vue2/public/mavon-editor/katex/contrib/copy-tex.css

@@ -0,0 +1,14 @@
+/* Force selection of entire .katex/.katex-display blocks, so that we can
+ * copy/paste the entire source code.  If you omit this CSS, partial
+ * selections of a formula will work, but will copy the ugly HTML
+ * representation instead of the LaTeX source code.  (Full selections will
+ * still produce the LaTeX source code.)
+ */
+.katex,
+.katex-display {
+    user-select: all;
+    -moz-user-select: all;
+    -webkit-user-select: all;
+    -ms-user-select: all;
+}
+