Android in-app purchases should have more details on query results

**Your Godot version:**
3.3 rc6

**Issue description:**
I've been implementing IAPs for a mobile game and felt like some details are missing in the official tutorial. When querying SKU details, you receive back a Dictionary of purchase info. My problem is that it's not mentioned in the tutorial what does this Dictionary contain exactly. I had to browse obscure Google Billing reference pages to find it.

Either the tutorial should specify what to expect in the response or at least link to the relevant page where user can find the information.

The relevant contents of the query info is:
- `is_acknowledged`: whether the purchase was acknowledged
- `is_auto_renewing`: whether subscription is active
- `purchase_state`: 1 if purchased, 2 if pending
- `purchase_token`: the token mentioned in the tutorial
- `purchase_time`: UNIX timestamp in milliseconds
- `sku`: ID of the purchasable item

**URL to the documentation page:**
https://docs.godotengine.org/en/latest/tutorials/platform/android/android_in_app_purchases.html