feat:add markdown

lua/plugins/extras/markdown.lua

@@ -0,0 +1,11 @@
+-- preview markdown
+-- https://github.com/iamcco/markdown-preview.nvim
+
+return {
+  'iamcco/markdown-preview.nvim',
+  cmd = { 'MarkdownPreviewToggle', 'MarkdownPreview', 'MarkdownPreviewStop' },
+  ft = { 'markdown' },
+  build = function()
+    vim.fn['mkdp#util#install']()
+  end,
+}