Fix typos in the HMR and Fast Refresh section of the 10up-toolkit readme

[marcoluzi]

Related Issue/RFC: #364

Description of the Change

Fixing syntax errors in the HMR and Fast Refresh section of the toolkit README.md.

Checklist:

• I have read the CONTRIBUTING document.
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my change.
• All new and existing tests passed.
• I have added a changeset to my PR. See CONTRIBUTING document for instructions

[changeset-bot]

⚠️ No Changeset found

Latest commit: 98a28bf

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