Documentation request for known issues

[brandonmlyon]

It would be great if we could add a section for known issues to the Umami docs website, or maybe add this to the FAQ:

1. When using a tag manager to add Umami to a site, the script needs access to document.write.
   1. If you are receiving a 400 error analytics.umami.is/api/send:1 Failed to load resource: the server responded with a status of 400 (), try enabling document.write access in your tag manager.