feat(plugins): Add file tree, Enable Lazy loading

I've tried to lazy load most the plugins to improve start up time.
It has been greatly reduced, from more than 600ms to just around 100ms

Bug: Line that shows up when you are inside a block(block-line) doesn't
have color.

lua/kickstart/plugins/nvim-tree.lua

@@ -0,0 +1,33 @@
+return {
+  "nvim-tree/nvim-tree.lua",
+  lazy = 'true',
+  cmd = { 'NvimTreeToggle', 'NvimTreeOpen' },
+  keys = {
+    { '<S-t>', '<cmd>NvimTreeToggle .<CR>', { noremap = true, silent = true } }
+  },
+  dependencies = {
+    "nvim-lua/plenary.nvim",
+    "nvim-tree/nvim-web-devicons", -- not strictly required, but recommended
+    "MunifTanjim/nui.nvim",
+  },
+  --[[ init = function()
+    vim.api.nvim_create_autocmd('BufEnter', {
+      pattern = 'NvimTree',
+      command = ":lua require('gitsigns').detach()"
+    })
+  end, ]]
+  opts = {
+    sort = {
+      sorter = "case_sensitive",
+    },
+    view = {
+      width = 38,
+    },
+    renderer = {
+      group_empty = true,
+    },
+    filters = {
+      dotfiles = true,
+    },
+  },
+}