markdown: add plugin for markdown formatting in view mode

lua/plugins/markdown.lua

@@ -0,0 +1,8 @@
+return {
+  {
+    "MeanderingProgrammer/markdown.nvim",
+    name = "render-markdown", -- Only needed if you have another plugin named markdown.nvim
+    dependencies = { "nvim-treesitter/nvim-treesitter" },
+    config = function() require("render-markdown").setup {} end,
+  },
+}