Add react-dom as an optional dependency

[amanteaux]

Currenty batchingForReactDom.js references react-dom even through react-dom is not referenced in the project package.json file.

It seems to cause an issue with recent versions of Yarn.

Would it be possible to react-dom to the optional dependencies of the package.json file? And I guess it should be the same with react-native.

Here is the full error from Yarn:

errors: [
  {
    detail: undefined,
    id: '',
    location: {
      column: 25,
      file: '../.yarn/__virtual__/micro-observables-virtual-7722fe8c8c/0/cache/micro-observables-npm-1.7.2-8e88bfdb52-15dd9eadc5.zip/node_modules/micro-observables/batchingForRea
ctDom.js',
      length: 11,
      line: 1,
      lineText: 'const ReactDOM = require("react-dom");',
      namespace: '',
      suggestion: ''
    },
    notes: [
      {
        location: {
          column: 33,
          file: '../.pnp.cjs',
          length: 343,
          line: 9047,
          lineText: '          "packageDependencies": [\\',
          namespace: '',
          suggestion: ''
        },
        text: `The Yarn Plug'n'Play manifest forbids importing "react-dom" here because it's not listed as a dependency of this package:`
      },
      {
        location: null,
        text: 'You can mark the path "react-dom" as external to exclude it from the bundle, which will remove this error. You can also surround this "require" call with a try/cat
ch block to handle this failure at run-time instead of bundle-time.'
      }
    ],
    pluginName: '',
    text: 'Could not resolve "react-dom"'
  }
]

[amanteaux]

Until this is solved in micro-observables, this issue can be mitigated through the .yarnrc.yml file by adding:

packageExtensions:
  micro-observables@*:
    dependencies:
      react-dom: "*"