feat(clipboard): initial support (#279)

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

lua/avante/clipboard/init.lua

@@ -0,0 +1,27 @@
+---NOTE: this module is inspired by https://github.com/HakonHarnes/img-clip.nvim/tree/main
+
+local Utils = require("avante.utils")
+
+---@class AvanteClipboard
+---@field clip_cmd string
+---@field get_clip_cmd fun(): string
+---@field has_content fun(): boolean
+---@field get_content fun(): string
+---
+---@class avante.Clipboard: AvanteClipboard
+local M = {}
+
+return setmetatable(M, {
+  __index = function(t, k)
+    local os_mapping = Utils.get_os_name()
+    ---@type AvanteClipboard
+    local impl = require("avante.clipboard." .. os_mapping)
+    if impl[k] ~= nil then
+      return impl[k]
+    elseif t[k] ~= nil then
+      return t[k]
+    else
+      error("Failed to find clipboard implementation for " .. os_mapping)
+    end
+  end,
+})