global: enable flask-debugtoolbar

[slint]

For the Flask-Debugtoolbar extension to work, it must also be added the invenio_base.apps entrypoints

Another problem though is that CSP headers are not playing well with the extension: pallets-eco/flask-debugtoolbar#88

[dinosk]

The issue was opened in 2015 so I don't think it'll be fixed with the suggestion mentioned there. We could maybe turn off CSP for debug mode, or set it to allow inline javascript https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/script-src?