Adding schema info to theme.json reference (#40599)

Received feedback from a developer that including a reference to the theme.json schema would go a long way as it's common for developers to rely on a reference over a how to guide.

docs/reference-guides/theme-json-reference/theme-json-living.md

@@ -4,7 +4,13 @@
 >
 > There're related documents you may be interested in: the [theme.json v1](/docs/reference-guides/theme-json-reference/theme-json-v1.md) specification and the [reference to migrate from theme.json v1 to v2](/docs/reference-guides/theme-json-reference/theme-json-migrations.md).
 
-This reference guide lists the settings and style properties defined in the theme.json schema. See the [theme.json how to guide](/docs/how-to-guides/themes/theme-json.md) for examples and guide on how to use the theme.json file in your theme.
+This reference guide lists the settings and style properties defined in the theme.json schema. See the [theme.json how to guide](/docs/how-to-guides/themes/theme-json.md) for examples and guide on how to use the theme.json file in your theme. 
+
+## Schema
+
+It can be difficult to remember the theme.json settings and properties while you develop, so a JSON scheme was created to help. The schema is available at https://schemas.wp.org/trunk/theme.json
+
+Code editors can pick up the schema and can provide help like tooltips, autocomplete, or schema validation in the editor. To use the schema in Visual Studio Code, add "$schema": "https://schemas.wp.org/trunk/theme.json" to the beginning of your theme.json file.
 
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 ## Settings