fix(wasm): Check for browser bundle existence before running tests (#4074)
fix(wasm): Check for browser bundle existence before running tests (#4074)

As of https://github.com/getsentry/sentry-javascript/pull/4048, it's more likely that one might try to run the full test suite without having built the browser bundle. Since the wasm tests rely on it, this adds a check before they run, along with an error message letting the user know why things aren't working.
getsentry/raven-js,getsentry/raven-js,getsentry/raven-js,getsentry/raven-js