Add `getBuildingId()` method to Widget API

[jonatanjacobsson]

Currently, there's no direct way to retrieve the building ID from the Widget API. Widgets need to query objects or parse URLs to determine which building they're operating in.

Proposed Solution:

Add a getBuildingId() method that returns the current building ID:

const buildingId = await window.StreamBIM.getBuildingId();
// Returns: "1000" (or current building ID)

Current Workaround:

Widgets must:

1. Parse URL parameters (buildingId=1000)
2. Query an object via getObjectInfo() and extract building property

Use Case:

Widget needs to make IFC search queries that require buildingId parameter. Having direct access would simplify widget development and make code more maintainable 👌

[chrhenne]

Good call! We will add this, staged for our 28/11 release.