Eslint: upgrade to version 8.0.0

See:

- https://eslint.org/blog/2021/10/eslint-v8.0.0-released
- https://eslint.org/docs/user-guide/migrating-to-8.0.0

Known unresolved issues (with low impact )that we decided to accept:

- mysticatea/eslint-plugin-node#301

Known issues that need to be fixed first:

- [x] wait for import-js/eslint-plugin-import#2191 to be released and merged here
- [x] wait for gajus/eslint-plugin-flowtype#496 to be released and merged here
- [x] wait for testing-library/eslint-plugin-testing-library#462 to be released and merged here
- [ ] ~wait for mysticatea/eslint-plugin-node#294 to be released and merged here~ replaced (probably temporarily) with `eslint-plugin-n` which supports Eslint 8
- [x] wait for facebook/react#22248 to be released and merged here
- [x] release minor/patch version of Adeira Eslint Config before merging this breaking change
- [x] switch `NEXT_VERSION_ERROR` to `ERROR` (adeira/universe#3625)

adeira-source-id: b194be7e4f2fc10d51a10ed8753c440414e36b4d

src/__tests__/SignedSource.test.js

@@ -5,11 +5,11 @@ import os from 'os';
 import SignedSource from '../SignedSource';
 
 test('signFile', () => {
-  expect(SignedSource.signFile(`# ${SignedSource.getSigningToken()}\ntest 1`)).toEqual(
+  expect(SignedSource.signFile(`# ${SignedSource.getSigningToken()}\ntest 1`)).toBe(
     `# @generated SignedSource<<d9b7b52f54978f54b84a0fd48145e470>>${os.EOL}test 1`,
   );
 
-  expect(SignedSource.signFile(`# ${SignedSource.getSigningToken()}\ntest 2`)).toEqual(
+  expect(SignedSource.signFile(`# ${SignedSource.getSigningToken()}\ntest 2`)).toBe(
     `# @generated SignedSource<<4c0c1ae4f5863c72731b2f543e830fd5>>${os.EOL}test 2`,
   );
 
@@ -18,7 +18,7 @@ test('signFile', () => {
     SignedSource.signFile(
       `# @generated SignedSource<<eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee>>\nalready signed test`,
     ),
-  ).toEqual(`# @generated SignedSource<<54e8ffafff15a19f858d95c9a13d5b1d>>\nalready signed test`);
+  ).toBe(`# @generated SignedSource<<54e8ffafff15a19f858d95c9a13d5b1d>>\nalready signed test`);
 
   expect(() =>
     SignedSource.signFile(`signature missing, no sign token`),