build(ui): Enable css sourcemaps (#6579)
build(ui): Enable css sourcemaps (#6579)

* build(ui): Enable css sourcemaps

* build(ui): Configure CSS sourcemaps via env variable

Make CSS sourcemaps off by default due to performance concerns

gencer/sentry,beeftornado/sentry,mvaled/sentry,gencer/sentry,ifduyue/sentry,looker/sentry,looker/sentry,ifduyue/sentry,beeftornado/sentry,looker/sentry,gencer/sentry,ifduyue/sentry,looker/sentry,mvaled/sentry,ifduyue/sentry,looker/sentry,gencer/sentry,gencer/sentry,mvaled/sentry,mvaled/sentry,mvaled/sentry,beeftornado/sentry,ifduyue/sentry,mvaled/sentry