docs: Add missing doc

docs/docs/reference/typescript-api/configuration/entity-id-decorator.md

@@ -0,0 +1,28 @@
+---
+title: "EntityId Decorator"
+isDefaultIndex: false
+generated: true
+---
+<!-- This file was generated from the Vendure source. Do not modify. Instead, re-run the "docs:build" script -->
+import MemberInfo from '@site/src/components/MemberInfo';
+import GenerationInfo from '@site/src/components/GenerationInfo';
+import MemberDescription from '@site/src/components/MemberDescription';
+
+
+## EntityId
+
+<GenerationInfo sourceFile="packages/core/src/entity/entity-id.decorator.ts" sourceLine="41" packageName="@vendure/core" />
+
+Decorates a property which points to another entity by ID. This custom decorator is needed
+because we do not know the data type of the ID column until runtime, when we have access
+to the configured EntityIdStrategy.
+
+```ts title="Signature"
+function EntityId(options?: IdColumnOptions): void
+```
+Parameters
+
+### options
+
+<MemberInfo kind="parameter" type={`IdColumnOptions`} />
+