Integrate with external services #71
Description
Inspired by
If to add all kinds of hooks into dandi archive etc, we better also then expose integration with external services like we already do for datasets.datalad.org and dandi-archive. To the moment we do not have unified registry (as originally wished for in https://github.com/con/external-services) but we have a growing number in dandi-archive at https://github.com/dandi/dandi-archive/blob/HEAD/web/src/views/FileBrowserView/FileBrowser.vue#L319 -- would just need to be extracted from Vue into json for reuse.