Fix: Keep empty lines in discussion tree (#173)

* Docs: Fix typos and remove trailing spaces

* Fix: Split strings by new lines correctly

* Docs: Recommend breakindent option to improve tree nodes indentation

* Fix: Replace whole buffer when creating a new suggestion

Previously, a trailing empty line was left in the buffer.

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Co-authored-by: Jakub Bortlík <jakub.bortlik@phonexia.com>

lua/gitlab/utils/init.lua

@@ -148,6 +148,16 @@ M.trim = function(s)
   return res
 end
 
+---Splits a string by new lines and returns an iterator
+---@param s string The string to split
+---@return table: An iterator object
+M.split_by_new_lines = function(s)
+  if s:sub(-1) ~= "\n" then
+    s = s .. "\n"
+  end -- Append a new line to the string, if there's none, otherwise the last line would be lost.
+  return s:gmatch("(.-)\n") -- Match 0 or more (as few as possible) characters followed by a new line.
+end
+
 -- Reverses the order of elements in a list
 ---@param list table The list to reverse
 ---@return table