Fix browser console errors

[KevinEtchells]

Context

While working on something else, I noticed a couple of browser console errors:

• The gov.uk inline script is being blocked by our Content Security Policy (meaning no gov.uk javascript is running)
• Missing manifest.json file

This update addresses both of these issues.

Changes proposed in this pull request

• Update the CSP to allow the inline script (but only this inline script) by using a hash
• Add the manifest.json file to the project. This alone didn't fully fix the problem, but removing the whitespace from the URL did

Guidance to review

• Visit any page and check there are no browser console errors
• Please look at the CSP changes in settings.py to confirm they are sensible

[gecBurton]

good spot!