Added analytics_events tinybird datasource

ref https://linear.app/tryghost/issue/ANAL-27/setup-tinybird-project-and-cicd
ref https://www.tinybird.co/docs/concepts/data-sources

- This is our main datasource, where we'll store events that come in as people browse around Ghost
- It's defined using tinybird's format, and then deployed out to tinybird using `tb deploy`

ghost/tinybird/datasources/analytics_events.datasource

@@ -0,0 +1,14 @@
+DESCRIPTION >
+    Analytics events landing data source
+
+SCHEMA >
+    `timestamp` DateTime `json:$.timestamp`,
+    `session_id` String `json:$.session_id`,
+    `action` LowCardinality(String) `json:$.action`,
+    `version` LowCardinality(String) `json:$.version`,
+    `payload` String `json:$.payload`
+
+ENGINE MergeTree
+ENGINE_PARTITION_KEY toYYYYMM(timestamp)
+ENGINE_SORTING_KEY timestamp
+ENGINE_TTL timestamp + toIntervalDay(60)