fix: #138 Missing worker policy when launching assistant

[smarinier]

See also nextcloud/server#39849

[julien-nc]

Hi,
Thanks a lot for the PR.
I can reproduce on Chromium but everything works fine on Firefox, there's only this console error message: Content-Security-Policy: The page’s settings blocked a worker script (worker-src) at blob:https://nextcloud.local/a9f6a3b5-2522-4efe-939a-28a3a33ba63f from being executed because it violates the following directive: “worker-src 'self'”