nvim: Change markdown_preview build process

nvim/.config/nvim/lua/plugins/markdown_preview.lua

@@ -1,5 +1,5 @@
 return {
-    {
+    -- Install markdown preview, use npx if available.
     "iamcco/markdown-preview.nvim",
     cmd = {
         "MarkdownPreviewToggle",
@@ -9,7 +9,19 @@ return {
     ft = {
         "markdown"
     },
-        build = function() vim.fn["mkdp#util#install"]() end
+    build = function(plugin)
+        if vim.fn.executable "npx" then
+            vim.cmd("!cd " .. plugin.dir .. " && cd app && npx --yes yarn install")
+        else
+            vim.cmd [[Lazy load markdown-preview.nvim]]
+            vim.fn["mkdp#util#install"]()
+        end
+    end,
+    init = function()
+        if vim.fn.executable "npx" then
+            vim.g.mkdp_filetypes = {
+                "markdown"
             }
-
+        end
+    end
 }