Add support for the administration javascript code

[nickygerritsen]

Please describe the feature you would like to see implemented.

I know the project is very new, so I am not expecting this to happen soon, but it would be nice if we could also integrate Sentry into the administration javascript code.

I think for this we need:

• A way to expose the DSN, release and environment to the javascript code. Maybe an admin controller?
• Inject the Sentry javascript SDK into the admin.
• Start the SDK and pass the correct DSN, release and environment.

[shyim]

When you want to make a PR, feel free to do so. It should be just configureable and disabled by default 👍

[nickygerritsen]

Any pointers where I should start, especially in the javascript part? Where / how should I inject/start the Sentry SDK? For the backend code to expose the DSN, release and environment I think I will manage.