v1.8.0

Updated metric alert to include integration id for slack action (#39)

* feat: add integration ID to metric alert

* docs: add more docs

* Update docs/index.md

* Update docs/resources/metric_alert.md

* Update sentry/resource_sentry_metric_alert.go

* Update sentry/resource_sentry_metric_alert_test.go

* deps: use 1.4.2 of go-sentry