chore: Create a story for UnitInput component (#25225)

## **Description**

This pull request adds a Storybook story for the `UnitInput` component.
The story renders the `UnitInput` component with several configurable
properties, allowing users to interact with and test the component in
isolation. The story adheres to the project's standards and provides a
clear example of how the `UnitInput` component can be used.

## **Related issues**

## **Manual testing steps**

- Go to the latest build of storybook in this PR
- Navigate to the UnitInput component in the Components/UI folder.

## **Screenshots/Recordings**


![25b39d33-9c39-40ba-a069-4fea28f1c58f](https://github.com/Devin-Applications/metamask-extension-devin/assets/168687171/556acccc-5c5b-4b6c-98a6-84060e19accb)

## **Pre-merge author checklist**

- [X] I’ve followed [MetaMask Coding
Standards](https://github.com/MetaMask/metamask-extension/blob/develop/.github/guidelines/CODING_GUIDELINES.md).
- [X] I've completed the PR template to the best of my ability
- [X] I’ve included tests if applicable
- [X] I’ve documented my code using [JSDoc](https://jsdoc.app/) format
if applicable
- [X] I’ve applied the right labels on the PR (see [labeling
guidelines](https://github.com/MetaMask/metamask-extension/blob/develop/.github/guidelines/LABELING_GUIDELINES.md)).
Not required for external contributors.

## **Pre-merge reviewer checklist**

- [ ] I've manually tested the PR (e.g. pull and build branch, run the
app, test code being changed).
- [ ] I confirm that this PR addresses all acceptance criteria described
in the ticket it closes and includes the necessary testing evidence such
as recordings and or screenshots.

[Devin
Run](https://preview.devin.ai/devin/de2457c56b42469f836e510b6d0b11fc)

---------

Co-authored-by: devin-ai-integration[bot] <158243242+devin-ai-integration[bot]@users.noreply.github.com>

ui/components/ui/unit-input/unit-input.stories.tsx

@@ -0,0 +1,43 @@
+import React from 'react';
+import type { Meta, StoryObj } from '@storybook/react';
+import UnitInput from './unit-input.component';
+
+const meta: Meta<typeof UnitInput> = {
+  title: 'Components/UI/UnitInput',
+  component: UnitInput,
+  argTypes: {
+    className: { control: 'text' },
+    dataTestId: { control: 'text' },
+    children: { control: 'text' },
+    actionComponent: { control: 'text' },
+    error: { control: 'boolean' },
+    onChange: { action: 'changed' },
+    onBlur: { action: 'blurred' },
+    placeholder: { control: 'text' },
+    suffix: { control: 'text' },
+    hideSuffix: { control: 'boolean' },
+    value: { control: 'text' },
+    keyPressRegex: { control: 'text' },
+    isDisabled: { control: 'boolean' },
+    isFocusOnInput: { control: 'boolean' },
+  },
+  args: {
+    className: '',
+    dataTestId: 'unit-input',
+    children: '',
+    actionComponent: '',
+    error: false,
+    placeholder: '0',
+    suffix: 'ETH',
+    hideSuffix: false,
+    value: '',
+    keyPressRegex: /^\d*(\.|,)?\d*$/u,
+    isDisabled: false,
+    isFocusOnInput: false,
+  },
+};
+
+export default meta;
+type Story = StoryObj<typeof UnitInput>;
+
+export const Default: Story = {};