feat(cfg): add prettierd formatting on save

lua/custom/plugins/prettier.lua

@@ -0,0 +1,43 @@
+return {
+    'MunifTanjim/prettier.nvim',
+
+    config = function()
+
+        local prettier = require("prettier")
+
+        prettier.setup({
+            bin = 'prettier', -- or `'prettierd'` (v0.23.3+)
+            filetypes = {
+                "css",
+                "graphql",
+                "html",
+                "javascript",
+                "javascriptreact",
+                "json",
+                "less",
+                "markdown",
+                "scss",
+                "typescript",
+                "typescriptreact",
+                "yaml",
+            },
+        })
+
+        prettier.setup({
+            ["null-ls"] = {
+                condition = function()
+                    return prettier.config_exists({
+                        -- if `false`, skips checking `package.json` for `"prettier"` key
+                        check_package_json = true,
+                    })
+                end,
+                runtime_condition = function(params)
+                    -- return false to skip running prettier
+                    return true
+                end,
+                timeout = 5000,
+            }
+        })
+
+    end,
+}