[Typo] in README.md fixtures -> fixture

[Ebazhanov]

Hello, Team!

This PR about fixing typo inside README.file
During my last installation, I found this issue when I was doing copy/paste of this block

const special = 'file.spss';
cy.fixtures(special, 'binary')
  .then(Cypress.Blob.binaryStringToBlob)
  .then((fileContent) => {
    cy.get('[data-cy="file-input"]').attachFile({ fileContent, filePath: special, encoding: 'utf-8' });
})

as you can see fixtures word is in plural form but should be in single according to the cypress documentation and

and inside the library

So it is the only way to make it work to use single form fixture

@abramenal thank you in advance for approving!

Best
Zhenja

[josephzidell]

@Ebazhanov Thank you for contributing!

[josephzidell]

@all-contributors add @Ebazhanov for code

[allcontributors]

@josephzidell

I've put up a pull request to add @Ebazhanov! 🎉