docs: make widget docs editable (#1782)

* make widget docs editable

* update widget doc frontmatter keys

* improve docs preview

* fix formatting

* fix preview

* add prism highlighting for previews

* fix formatting

* restore cms branch

website/content/docs/widgets.md

@@ -0,0 +1,29 @@
+---
+title: Widgets
+weight: 30
+group: reference
+---
+
+Widgets define the data type and interface for entry fields. Netlify CMS comes with several built-in widgets. Click the widget names in the sidebar to jump to specific widget details. We’re always adding new widgets, and you can also [create your own](../custom-widgets)!
+
+Widgets are specified as collection fields in the Netlify CMS `config.yml` file. Note that [YAML syntax](https://en.wikipedia.org/wiki/YAML#Basic_components) allows lists and objects to be written in block or inline style, and the code samples below include a mix of both.
+
+To see working examples of all of the built-in widgets, try making a 'Kitchen Sink' collection item on the [CMS demo site](https://cms-demo.netlify.com). (No login required: click the login button and the CMS will open.) You can refer to the demo [configuration code](https://github.com/netlify/netlify-cms/blob/master/dev-test/config.yml) to see how each field was configured.
+
+
+## Common widget options
+
+The following options are available on all fields:
+
+- `required`: specify as `false` to make a field optional; defaults to `true`
+- `hint`: optionally add helper text directly below a widget. Useful for including instructions.
+- `pattern`: add field validation by specifying a list with a [regex pattern](https://regexr.com/) and an error message; more extensive validation can be achieved with [custom widgets](../custom-widgets/#advanced-field-validation)
+  - **Example:**
+        ```yaml
+        - label: "Title"
+          name: "title"
+          widget: "string"
+          pattern: [".{12,}", "Must have at least 12 characters"]
+        ```
+
+## Default widgets