Move deprecated eslintrc plugin configs to flat config

[devtobi]

To move to ESLint flat config the following dependencies need to support this feature:

• eslint:recommended -> @eslint/js
• plugin:vue/vue3-essential -> eslint-plugin-vue
• @vue/eslint-config-typescript -> WAITING FOR SUPPORT (see Flat config support vuejs/eslint-config-typescript#72)
• @vue/eslint-config-prettier/skip-formatting -> WAITING FOR SUPPORT (see Eslint 9.0 released and the flat configuration format vuejs/eslint-config-prettier#19)
• plugin:@intlify/vue-i18n/recommended -> @intlify/eslint-plugin-vue-i18n

With the new flat config syntax rushstack/eslint-patch can be removed. ;)

[devtobi]

By using FlatCompat existing eslintrc configurations can be reused in flat config style. This is a great solution while waiting for the packages to provide flat config configurations

[devtobi]

Support is now available, however still waiting for new stable major releases. Currently only RC candidates are available.

[devtobi]

Releases got published, can start this migration now.