Merge branch 'add-manifest-src-to-csp' into 'develop'

Add manifest-src to CSP to allow manifest.json

See merge request pleroma/pleroma!474

lib/pleroma/plugs/http_security_plug.ex

@@ -39,6 +39,7 @@ defmodule Pleroma.Plugs.HTTPSecurityPlug do
       "font-src 'self'",
       "script-src 'self'",
       "connect-src 'self' " <> String.replace(Pleroma.Web.Endpoint.static_url(), "http", "ws"),
+      "manifest-src 'self'",
       "upgrade-insecure-requests"
     ]
     |> Enum.join("; ")