CSP Integration - clarify documentation

[codebyuma]

We received some feedback through Zendesk to clarify and/or correct the readme documentation:

1. Clarify that the integration won't work while a split test is enabled

   • This is a known limitation that requests to sites with split testing enabled won't execute edge functions, but we should make it clear that the EF limitations apply to this integration.

2. Update the documentation for path to resolve a markdown error and clarify what the default value is/does.

   • Right now, it says the default is

     "/_".*

[stuckj]

Number 2 in that list above is confusing me right now. After enabling the integration for my site I'm not seeing the header added anywhere. I thought, perhaps, I needed to put something in here beyond the default, but nothing I use appears to be working.

[stuckj]

Using /* worked for me.