chore(deps): update storybook to v5.3.18

[thi-bot]

This PR contains the following updates:

Package	Update	Type	Change	Sourcegraph
@storybook/addon-storyshots	patch	devDependencies	5.3.17 -> 5.3.18
@storybook/addon-viewport	patch	devDependencies	5.3.17 -> 5.3.18
@storybook/react	patch	devDependencies	5.3.17 -> 5.3.18

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Release Notes

storybookjs/storybook

### [`v5.3.18`](https://togithub.com/storybookjs/storybook/blob/master/CHANGELOG.md#​5318-March-31-2020) [Compare Source](https://togithub.com/storybookjs/storybook/compare/v5.3.17...v5.3.18) ##### Bug Fixes - Core: Fix manager assets to be routed in express ([#​9646](https://togithub.com/storybookjs/storybook/pull/9646)) - Storyshots: Fix MDX transform ([#​10223](https://togithub.com/storybookjs/storybook/pull/10223)) - Addon-docs: Restore IE11 compat on Windows by transpiling acorn-jsx ([#​9790](https://togithub.com/storybookjs/storybook/pull/9790)) - Addon-docs: Ensure visibility of links within prop descriptions ([#​10210](https://togithub.com/storybookjs/storybook/pull/10210))

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