[New docs] Create stories for components starting with the letters M-O

[tkajtoch]

Summary

Create Storybook playground stories for EUI components whose names start with the letters M, N, and O. This is a part of #7405.

Components to create stories for:

• [ ] EuiMark
• [ ] EuiMarkdownEditor
• [ ] EuiMarkdownFormat
• [ ] EuiModal
• [ ] EuiConfirmModal
• [ ] EuiModalFooter
• [ ] EuiModalHeader
• [ ] EuiModalBody
• [ ] EuiModalHeaderTitle
• [ ] EuiResizeObserver
• [ ] EuiMutationObserver
• [ ] EuiOutsideClickDetector
• [ ] EuiOverlayMask

Acceptance Criteria

• Playground stories are created following the default story file format we're using
• Story controls include all component props
  • If some props are complicated to get added, feel free to leave a TODO comment for now instead

Story file template

import React from 'react';
import type { Meta, StoryObj } from '@storybook/react';

const meta: Meta<COMPONENT_PROPS> = { // TODO: Replace COMPONENT_PROPS with the component props type
  title: 'Components/COMPONENT_EXPORT_NAME', // TODO: Replace COMPONENT_EXPORT_NAME with component export name
  component: COMPONENT, // TODO: Replace with the actual component import
  argTypes: {} // TODO: Setup arg types,
  args: {}, // TODO: Pass in default args
};

export default meta;
type Story = StoryObj<COMPONENT_PROPS>; // TODO: Replace COMPONENT_PROPS with the component props type

export const Default: Story = {};