Add markdown preview, update rust.vim

sources_non_forked/markdown-preview.nvim/app/pages/meta.js

@@ -0,0 +1,25 @@
+import getRender from 'md-it-meta/lib/meta'
+
+export const meta = separates  => {
+  if (separates === void 0) {
+    separates = [['---'], ['---']]
+  }
+  return (md) => {
+    const render = getRender(md, separates)
+    md.meta = md.meta || {}
+    md.block.ruler.before(
+      'code',
+      'meta',
+      (...args) => {
+        try {
+          return render(...args)
+        } catch(e) {
+          console.log('md-it-meta', e)
+        }
+      },
+      {
+        alt: []
+      }
+    );
+  };
+}