feat: allow padding as a function

Now a function can be given for `padding` which can return a boolean.
This will allow commenting in `norg` files. Previously it wasn't
possible because of it's strict commenting rules.

```lua
require('Comment').setup({
    padding = function ()
        return vim.bo.filetype ~= 'norg'
    end
})
````

Author: numToStr

README.md

@@ -67,7 +67,7 @@ Following are the **default** config for the [`setup()`](#setup). If you want to
 ```lua
 {
     ---Add a space b/w comment and the line
-    ---@type boolean
+    ---@type boolean|fun():boolean
     padding = true,
 
     ---Whether the cursor should stay at its position

lua/Comment/utils.lua

@@ -66,11 +66,11 @@ end
 
 ---Helper to get padding (I was tired to check this everywhere)
 ---NOTE: We can also use function to calculate padding if someone wants more spacing
----@param flag boolean
+---@param flag boolean|fun():boolean
 ---@return string string Padding chars
 ---@return string string Padding pattern
 function U.get_padding(flag)
-    if not flag then
+    if not U.is_fn(flag) then
         return '', ''
     end
     return ' ', '%s?'