Add docs

docs/how-to-guides/themes/theme-json.md

@@ -477,7 +477,9 @@ These are the current typography properties supported by blocks:
 
 There's a growing need to add more theme metadata to the theme.json. This section lists those other fields:
 
-**customTemplates**: within this field themes can list the custom templates present in the `block-templates` folder, the keys should match the custom template name. For example, for a custom template named `my-custom-template.html`, the `theme.json` can declare what post types can use it and what's the title to show the user:
+#### `customTemplates`: 
+
+within this field themes can list the custom templates present in the `block-templates` folder, the keys should match the custom template name. For example, for a custom template named `my-custom-template.html`, the `theme.json` can declare what post types can use it and what's the title to show the user:
 
 ```json
 {
@@ -490,6 +492,38 @@ There's a growing need to add more theme metadata to the theme.json. This sectio
 }
 ```
 
+#### `skipLinks`
+
+Within this field, themes can change the behavior of the automatic skip-link generation, or opt-out.
+
+```json
+{
+	"skipLinks": {
+		"auto": true,
+		"css": true,
+		"links": [
+			{
+				"target": "#skip-link-target",
+				"label": "Skip to Content"
+			},
+			{
+				"target": "#main-navigation",
+				"label": "Skip to Navigation",
+				"useFallbacks": false
+			}
+		]
+	}
+}
+```
+
+Arguments:
+* `auto`: (bool) Whether skip-links will be auto-generated or not. Defaults to `true`. To opt-out of the automatic skip-links, set to `false`.
+* `css:` (bool) Whether CSS for the skip-link should be automatically added or not. Defaults to `true`. To opt-out and manually handle CSS for skip-links, set to `false`.
+* `links`: (array) Can be used to define a custom skip-link (or multiple skip-links if needed). Each "link" can have the following:
+  * `target`: (string|array) The selector of the element that should be used as the target.
+  * `label`: (string) The skip-link's label. If omitted defaults to `Skip to content`.
+  * `useFallbacks`: (bool) Defaults to `true`. If a `target` is not defined, or the `target` element is not located, then the skip-link target will fallback to the 1st instance of these elements: `#skip-link-target, main, .wp-block-post-title, .wp-block-query-loop, .wp-block-post-content, .entry-content, h1, h2`. If set to false, then the fallbacks won't be added. Use in case of multiple skip-links.
+
 ## Frequently Asked Questions
 
 ### The naming schema of CSS Custom Properties