(core) forward more kinds of edits to a virtual table

Summary:
Some edits to virtual tables (such as webhook lists) happen
via a route that was not yet handled. Actually Cyprien (the
original author) had handled this case but it got removed
because I didn't know what it was for :-). This brings back
support for edits by this route.

Test Plan: added a test

Reviewers: georgegevoian

Reviewed By: georgegevoian

Differential Revision: https://phab.getgrist.com/D3924

app/common/DocActions.ts

@@ -90,11 +90,11 @@ export function isSchemaAction(action: DocAction):
   return SCHEMA_ACTIONS.has(action[0]);
 }
 
-export function isDataAction(action: DocAction):
+export function isDataAction(action: DocAction|UserAction):
     action is AddRecord | RemoveRecord | UpdateRecord |
               BulkAddRecord | BulkRemoveRecord | BulkUpdateRecord |
               ReplaceTableData | TableDataAction {
-  return DATA_ACTIONS.has(action[0]);
+  return DATA_ACTIONS.has(String(action[0]));
 }
 
 /**