fix(vue): Add vue-router to peer dependencies

[lobsterkatie]

We use vue-router in our router instrumentation for Vue. Presumably if you're using our Vue router instrumentation, you already have vue-router installed, but just to dot our I's and cross our T's, let's say out loud that it's necessary.

[github-actions]

size-limit report

Path	Size
@sentry/browser - CDN Bundle (gzipped)	20.23 KB (-0.01% 🔽)
@sentry/browser - Webpack	21.1 KB (0%)
@sentry/react - Webpack	21.12 KB (0%)
@sentry/browser + @sentry/tracing - CDN Bundle (gzipped)	27.39 KB (0%)