Storybook: Add LetterSpacingControl story

packages/block-editor/src/components/letter-spacing-control/stories/index.story.js

@@ -0,0 +1,75 @@
+/**
+ * Internal dependencies
+ */
+import LetterSpacingControl from '../';
+
+const meta = {
+	title: 'BlockEditor/LetterSpacingControl',
+	component: LetterSpacingControl,
+	parameters: {
+		docs: {
+			canvas: { sourceState: 'shown' },
+			description: {
+				component:
+					'The `LetterSpacingControl` component renders a UnitControl that lets the user enter a numeric value and select a unit, for example `px` or `rem`.',
+			},
+		},
+	},
+	argTypes: {
+		onChange: {
+			action: 'onChange',
+			description: 'A callback function invoked when the value is changed.',
+			table: {
+				type: {
+					summary: 'function',
+				},
+			},
+		},
+		value: {
+			control: {
+				type: null,
+			},
+			table: {
+				type: {
+					summary: 'number',
+				},
+			},
+			description: 'The current value of the letter spacing setting.',
+		},
+		__next40pxDefaultSize: {
+			control: {
+				type: 'boolean',
+			},
+			description:
+				'Defines the default size of elements within a block or component.',
+			table: {
+				type: {
+					summary: 'boolean',
+				},
+			},
+		},
+		__unstableInputWidth: {
+			description:
+				'Input width to pass through to inner UnitControl. Should be a valid CSS value.',
+			control: {
+				type: null,
+			},
+			table: {
+				type: {
+					summary: 'string|number|undefined',
+				},
+			},
+		},
+	},
+};
+
+export default meta;
+
+/**
+ * Default story shows the LetterSpacingControl.
+ */
+export const Default = {
+	args: {
+		value: 10,
+	},
+};