feat(indent-blankline): add which-key toggles (#4122)

## Description

Add which-key toggle mappings for toggling both the indention guides,
and also scope highlight on a per buffer basis.

## Screenshots


![2024-07-20_08-16](https://github.com/user-attachments/assets/7b282868-c035-4f71-97dd-5738cd953713)

## Checklist

- [x] I've read the
[CONTRIBUTING](https://github.com/LazyVim/LazyVim/blob/main/CONTRIBUTING.md)
guidelines.

---------

Co-authored-by: Folke Lemaitre <folke.lemaitre@gmail.com>

lua/lazyvim/plugins/ui.lua

@@ -225,7 +225,18 @@ return {
   {
     "lukas-reineke/indent-blankline.nvim",
     event = "LazyFile",
-    opts = {
+    opts = function()
+      LazyVim.toggle.map("<leader>ug", {
+        name = "Indention Guides",
+        get = function()
+          return require("ibl.config").get_config(0).enabled
+        end,
+        set = function(state)
+          require("ibl").setup_buffer(0, { enabled = state })
+        end,
+      })
+
+      return {
         indent = {
           char = "│",
           tab_char = "│",
@@ -246,7 +257,8 @@ return {
             "lazyterm",
           },
         },
-    },
+      }
+    end,
     main = "ibl",
   },