style: fixed some sumneko diagnostics error

lua/tokyonight/theme.lua

@@ -7,7 +7,7 @@ local M = {}
 ---@field fg string|nil
 ---@field bg string|nil
 ---@field sp string|nil
----@field style string|nil
+---@field style string|nil|Highlight
 
 ---@alias Highlights table<string,Highlight>
 

lua/tokyonight/util.lua

@@ -12,12 +12,12 @@ local function hexToRgb(c)
   return { tonumber(c:sub(2, 3), 16), tonumber(c:sub(4, 5), 16), tonumber(c:sub(6, 7), 16) }
 end
 
----@param fg string foreground color
----@param bg string background color
+---@param foreground string foreground color
+---@param background string background color
 ---@param alpha number number between 0 and 1. 0 results in bg, 1 results in fg
-function M.blend(fg, bg, alpha)
-  bg = hexToRgb(bg)
-  fg = hexToRgb(fg)
+function M.blend(foreground, background, alpha)
+  local bg = hexToRgb(background)
+  local fg = hexToRgb(foreground)
 
   local blendChannel = function(i)
     local ret = (alpha * fg[i] + ((1 - alpha) * bg[i]))