Add `@sentry/browser` to renovate

Problem

We want to upgrade the @sentry/browser package to 6.10.0 or higher. This could either be really simple, or very painful. We should do this by adding the package to renovate.

Things to consider

• We need to be very careful that this upgrade doesn't break our current processes
• We need to be careful this upgrade works with our self-hosted version of sentry
• We should make groupfoundations aware of this change (cc @mikegreiling)