refactor: Move debounce function to the utils

lua/symbols-outline/utils/init.lua

@@ -0,0 +1,19 @@
+local M = {}
+
+--- @param  f function
+--- @param  delay number
+--- @return function
+function M.debounce(f, delay)
+    local timer = vim.loop.new_timer()
+
+    return function (...)
+        local args = { ... }
+
+        timer:start(delay, 0, vim.schedule_wrap(function ()
+            timer:stop()
+            f(unpack(args))
+        end))
+    end
+end
+
+return M