feat(config): add `override_cwd` option to control cwd behavior

[xyaman]

I really like this plugin, but having it automatically override the current working directory has been inconvenient, as it affects other plugins and settings that rely on vim.fn.getcwd(), such as LSPs and fuzzy finders.

This PR adds a new configuration option: override_cwd. By default, it is set to true to preserve the existing behavior of changing working directory when opening dired.nvim. Setting it to false prevents dired from overriding the user’s cwd and instead uses the directory relative to the currently opened file, similar to netrw.