Prevent undefined this.$sentry while offline test

[c4ss]

What problem does this feature solve?

Currently this module will completely avoid creating this.$sentry when there is no DSN specified or the disabled option is flagged - this causes any this.$sentry.xxx functions to error and completely prevents offline debugging without sentry reporting.

For local testing no error reporting is necessary as the console log is accessible to us and will end up clogging issues being reporting from real users

What does the proposed changes look like?

serverless-sentry-lib achieves this by deleting the DSN and installing nonetheless (although this uses the deprecated Raven package).

_{This feature request is available on Nuxt community (#c40)}

[DiederikvandenB]

Hi, thanks for reporting. Would you be willing to open a PR for this?

[c4ss]

Have opened #48

[DiederikvandenB]

Thanks! I have some other commits I need to merge in too. On my todo for tonight or tomorrow.