fix compatibility with yarn 2

Based on good practices.

* #65 - add sassOptions for docs

fix docs with error: 'options has an unknown property 'indentedSyntax'.'
which new sass-loader are writen in 'sassOptions';
This should also cause quick prototyping's sass setting, after executing '$vue serve'

* #65 - sassOptions fix for sass-loader

* #65 - fix sassOptions - lang:ru

* add comment for sassOptions version

* add comment for sassOptions

* add comment for sassOptions

* Update docs/guide/pre-processors.md
Co-Authored-By: Haoqun Jiang <haoqunjiang@gmail.com>

* Update pre-processors.md

* Update pre-processors.md

It's a rather small change that does not affect vue-loader.
Updated to accommodate future bug fixes.

See https://github.com/vuejs/component-compiler-utils/blob/master/lib/templateCompilerModules/assetUrl.ts#L9

* [RU] Translation moved to VuePress

* custom-block.md example fix

* fix link

* options.md правка

* testing.md fix links

* linting.md fix link

* options.md added new section

* options.md add exposeFilename

* guide/README.md update

* README.md обновление

* docs: [RU] update

closes https://github.com/vuejs/vue-cli/issues/3399

* fix: keep index when filtering styles

* test: update test fixture to address issue

* [RU] Translation moved to VuePress

* custom-block.md example fix

* fix link

* options.md правка

* testing.md fix links

* linting.md fix link

* options.md added new section

* options.md add exposeFilename

* guide/README.md update

* README.md обновление

* docs(zh): update

* Apply suggestions from code review
Co-Authored-By: Jinjiang <zhaojinjiang@me.com>

closes #1435