replaced peek with markdown preview

lua/plugins/markdown-preview.lua

@@ -0,0 +1,19 @@
+return {
+  'iamcco/markdown-preview.nvim',
+  cmd = {
+    'MarkdownPreviewToggle',
+    'MarkdownPreview',
+    'MarkdownPreviewStop'
+  },
+  branch = 'master',
+  ft = { 'markdown' },
+  build = function()
+    vim.fn['mkdp#util#install']()
+  end,
+  init = function ()
+    vim.g.mkdp_auto_close = 0
+    vim.g.mkdp_auto_start = 1
+    vim.g.mkdp_combine_preview = 1
+    vim.g.mkdp_combine_preview_auto_refresh = 1
+  end
+}