update to ${param:TABLE_ID}_raw_changelog; add info about subcollection groups

Author: rachelsaunders

firestore-bigquery-export/POSTINSTALL.md

@@ -13,7 +13,7 @@ You can test out this extension right away:
 1.  Query your **raw changelog table**, which should contain a single log of creating the `bigquery-mirror-test` document.
 
     ```  
-    SELECT * FROM `${param:PROJECT_ID}.${param:DATASET_ID}.${param:COLLECTION_PATH}_raw_changelog`   
+    SELECT * FROM `${param:PROJECT_ID}.${param:DATASET_ID}.${param:TABLE_ID}_raw_changelog`   
     ```
 
 1.  Query your **latest view**, which should return the latest change event for the only document present -- `bigquery-mirror-test`.
@@ -28,7 +28,7 @@ The `bigquery-mirror-test` document will disappear from the **latest view** and
 1.  You can check the changelogs of a single document with this query:
 
     ```  
-    SELECT * FROM `${param:PROJECT_ID}.${param:DATASET_ID}.${param:COLLECTION_PATH}_raw_changelog` 
+    SELECT * FROM `${param:PROJECT_ID}.${param:DATASET_ID}.${param:TABLE_ID}_raw_changelog` 
        WHERE document_name = "bigquery-mirror-test" 
        ORDER BY TIMESTAMP ASC  
     ```
@@ -37,12 +37,12 @@ The `bigquery-mirror-test` document will disappear from the **latest view** and
 
 Whenever a document is created, updated, imported, or deleted in the specified collection, this extension sends that update to BigQuery. You can then run queries on this mirrored dataset which contains the following resources:
 
-+   **raw changelog table:** [`${param:DATASET_ID}_raw_changelog`](https://console.cloud.google.com/bigquery?project=${param:PROJECT_ID}&p=${param:PROJECT_ID}&d=${param:DATASET_ID}&t=${param:COLLECTION_PATH}_raw_changelog&page=table)
++   **raw changelog table:** [`${param:TABLE_ID}_raw_changelog`](https://console.cloud.google.com/bigquery?project=${param:PROJECT_ID}&p=${param:PROJECT_ID}&d=${param:DATASET_ID}&t=${param:TABLE_ID}_raw_changelog&page=table)
 +   **latest view:** [`${param:DATASET_ID}_raw_latest`](https://console.cloud.google.com/bigquery?project=${param:PROJECT_ID}&p=${param:PROJECT_ID}&d=${param:DATASET_ID}&t=${param:COLLECTION_PATH}_raw_latest&page=table)
 
 To review the schema for these two resources, click the **Schema** tab for each resource in BigQuery.
 
-Note that this extension only listens for _document_ changes in the collection, but not changes in any _subcollection_. You can, though, install additional instances of this extension to specifically listen to a subcollection or other collections in your database.
+Note that this extension only listens for _document_ changes in the collection, but not changes in any _subcollection_. You can, though, install additional instances of this extension to specifically listen to a subcollection or other collections in your database. Or if you have the same subcollection across documents in a given collection, you can use `{wildcard}` notation to listen to all those subcollections (for example: `chats/{chatid}/posts`).
 
 ### _(Optional)_ Import existing documents