feat(v2): Extract npm2yarn plugin (#3469)

* chore(v2): add dependency

* test(v2): Add npm2yarn tests

* feat(v2): Move npm2yarn to a new remark plugin

* remark npm2yarn plugin => ready to release

Co-authored-by: slorber <lorber.sebastien@gmail.com>

website/src/plugins/remark-npm2yarn.js

@@ -1,81 +0,0 @@
-/**
- * Copyright (c) Facebook, Inc. and its affiliates.
- *
- * This source code is licensed under the MIT license found in the
- * LICENSE file in the root directory of this source tree.
- */
-
-const npmToYarn = require('npm-to-yarn');
-
-// E.g. global install: 'npm i' -> 'yarn'
-const convertNpmToYarn = (npmCode) => npmToYarn(npmCode, 'yarn');
-
-const transformNode = (node) => {
-  const npmCode = node.value;
-  const yarnCode = convertNpmToYarn(node.value);
-  return [
-    {
-      type: 'jsx',
-      value:
-        `<Tabs groupId="npm2yarn" defaultValue="npm" ` +
-        `values={[
-    { label: 'npm', value: 'npm', },
-    { label: 'Yarn', value: 'yarn', },
-  ]}
->
-<TabItem value="npm">`,
-    },
-    {
-      type: node.type,
-      lang: node.lang,
-      value: npmCode,
-    },
-    {
-      type: 'jsx',
-      value: '</TabItem>\n<TabItem value="yarn">',
-    },
-    {
-      type: node.type,
-      lang: node.lang,
-      value: yarnCode,
-    },
-    {
-      type: 'jsx',
-      value: '</TabItem>\n</Tabs>',
-    },
-  ];
-};
-
-const matchNode = (node) => node.type === 'code' && node.meta === 'npm2yarn';
-const nodeForImport = {
-  type: 'import',
-  value:
-    "import Tabs from '@theme/Tabs';\nimport TabItem from '@theme/TabItem';",
-};
-
-module.exports = () => {
-  let transformed = false;
-  const transformer = (node) => {
-    if (matchNode(node)) {
-      transformed = true;
-      return transformNode(node);
-    }
-    if (Array.isArray(node.children)) {
-      let index = 0;
-      while (index < node.children.length) {
-        const result = transformer(node.children[index]);
-        if (result) {
-          node.children.splice(index, 1, ...result);
-          index += result.length;
-        } else {
-          index += 1;
-        }
-      }
-    }
-    if (node.type === 'root' && transformed) {
-      node.children.unshift(nodeForImport);
-    }
-    return null;
-  };
-  return transformer;
-};