feat: support usage as codecompanion extension

Author: franco-ruggeri

lua/codecompanion/_extensions/spinner/init.lua

@@ -0,0 +1,12 @@
+local codecompanion_spinner = require("codecompanion-spinner")
+
+---@class CodeCompanion.Extension
+---@field setup fun(opts: table) Function called when extension is loaded
+---@field exports? table Functions exposed via codecompanion.extensions.your_extension
+local M = {}
+
+function M.setup(opts)
+	codecompanion_spinner.setup(opts)
+end
+
+return M