fix(gatsby-plugin-typescript): typo in readme

[sshbio]

extra . caused npm install error

Description

Related Issues

[muescha]

Suggested change

	_**Please note**: If packages don't ship with TypeScript definitions you'll need to manually install those type definitions, e.g. for React. A typical Gatsby project would need: `npm install --save-dev @types/react @types/react-dom @types/node`_
	_**Please note**: If packages don't ship with TypeScript definitions you'll need to manually install those type definitions, e.g. for React. A typical Gatsby project would need:
	```shell
	npm install --save-dev @types/react @types/react-dom @types/node
	```

[LekoArts]

Thanks 👍

[gatsbot]

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