fix: only run updated checker for installed plugins. Fixes #16

lua/lazy/manage/checker.lua

@@ -16,6 +16,7 @@ end
 
 function M.fast_check()
   for _, plugin in pairs(Config.plugins) do
+    if plugin._.installed then
       plugin._.has_updates = nil
       local info = Git.info(plugin.dir)
       local target = Git.get_target(plugin)
@@ -23,6 +24,7 @@ function M.fast_check()
         plugin._.has_updates = true
       end
     end
+  end
   M.report()
 end