tailwindcss/src/plugins/alignSelf.js

export default function () {
  return function ({ addUtilities, variants }) {
    addUtilities(
      {
        '.self-auto': {
          'align-self': 'auto',
        },
        '.self-start': {
          'align-self': 'flex-start',
        },
        '.self-end': {
          'align-self': 'flex-end',
        },
        '.self-center': {
          'align-self': 'center',
        },
        '.self-stretch': {
          'align-self': 'stretch',
        },
      },
      variants('alignSelf')
    )
  }
}