Spelling correction in README.md

[garyray-k]

small spelling correction.

Please send your pull requests the develop branch.
Don't forget to add the change to CHANGELOG.md.

Note: Sometimes the development moves very fast. It is highly
recommended that you update your branch of develop before creating a
pull request to send us your changes. This makes everyone's lives
easier (including yours) and helps us out on the development team.
Thanks!

• Does the pull request solve a related issue?
• If so, can you reference the issue?
• What does the pull request accomplish? Use a list if needed.
• If it includes major visual changes please add screenshots.

[MagicMirrorBot]

	Warnings
⚠️	Please include an updated CHANGELOG.md file. This way we can keep track of all the contributions.

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