chore(clipboard): separate logic to save as base64 and files (#329)

Signed-off-by: Aaron Pham <contact@aarnphm.xyz>

lua/avante/clipboard/init.lua

@@ -1,16 +1,28 @@
 ---NOTE: this module is inspired by https://github.com/HakonHarnes/img-clip.nvim/tree/main
+---@see https://github.com/ekickx/clipboard-image.nvim/blob/main/lua/clipboard-image/paste.lua
 
+local Path = require("plenary.path")
 local Utils = require("avante.utils")
+local Config = require("avante.config")
 
 ---@class AvanteClipboard
 ---@field clip_cmd string
 ---@field get_clip_cmd fun(): string
 ---@field has_content fun(): boolean
----@field get_content fun(): string
+---@field get_base64_content fun(): string
+---@field save_content fun(filename: string): boolean
 ---
 ---@class avante.Clipboard: AvanteClipboard
 local M = {}
 
+M.paste_directory = Path:new(Config.history.storage_path):joinpath("pasted_images")
+
+M.setup = function()
+  if not M.paste_directory:exists() then
+    M.paste_directory:mkdir({ parent = true })
+  end
+end
+
 return setmetatable(M, {
   __index = function(t, k)
     local os_mapping = Utils.get_os_name()