Use babel standalone package (#723)

Though it isn't recommended, MDX often finds itself
being used on the client or other environmentts where
bundler configuration might not be customizable.

This switches to babel standalone to allow for better
support for those scenarios.

Before actually merging this it might be worthwhile to
add some benchmarking to ensure that this doesn't introduce
a performance regression (I'm not sure how standalone
works internally).

---

Closes #704

packages/mdx/mdx-hast-to-jsx.js

@@ -1,4 +1,4 @@
-const {transformSync} = require('@babel/core')
+const {transform} = require('@babel/standalone')
 const styleToObject = require('style-to-object')
 const camelCaseCSS = require('camelcase-css')
 const uniq = require('lodash.uniq')
@@ -102,7 +102,7 @@ MDXContent.isMDXComponent = true`
 
     // Check JSX nodes against imports
     const babelPluginExptractImportNamesInstance = new BabelPluginExtractImportNames()
-    transformSync(importStatements, {
+    transform(importStatements, {
       configFile: false,
       babelrc: false,
       plugins: [
@@ -116,7 +116,7 @@ MDXContent.isMDXComponent = true`
     const babelPluginApplyMdxPropInstance = new BabelPluginApplyMdxProp()
     const babelPluginApplyMdxPropToExportsInstance = new BabelPluginApplyMdxProp()
 
-    const fnPostMdxTypeProp = transformSync(fn, {
+    const fnPostMdxTypeProp = transform(fn, {
       configFile: false,
       babelrc: false,
       plugins: [
@@ -126,7 +126,7 @@ MDXContent.isMDXComponent = true`
       ]
     }).code
 
-    const exportStatementsPostMdxTypeProps = transformSync(exportStatements, {
+    const exportStatementsPostMdxTypeProps = transform(exportStatements, {
       configFile: false,
       babelrc: false,
       plugins: [

packages/mdx/package.json

@@ -29,9 +29,9 @@
     "mdx-hast-to-jsx.js"
   ],
   "dependencies": {
-    "@babel/core": "7.6.0",
     "@babel/plugin-syntax-jsx": "7.2.0",
     "@babel/plugin-syntax-object-rest-spread": "7.2.0",
+    "@babel/standalone": "7.6.0",
     "@mdx-js/util": "^1.4.5",
     "babel-plugin-apply-mdx-type-prop": "^1.4.5",
     "babel-plugin-extract-import-names": "^1.4.5",

packages/remark-mdx/extract-imports-and-exports.js

@@ -1,4 +1,4 @@
-const {transformSync} = require('@babel/core')
+const {transform} = require('@babel/standalone')
 const declare = require('@babel/helper-plugin-utils').declare
 
 const syntaxJsxPlugin = require('@babel/plugin-syntax-jsx')
@@ -48,7 +48,7 @@ const partitionString = (str, indices) =>
 module.exports = (value, vfile) => {
   const instance = new BabelPluginExtractImportsAndExports()
 
-  transformSync(value, {
+  transform(value, {
     plugins: [syntaxJsxPlugin, proposalObjectRestSpreadPlugin, instance.plugin],
     filename: vfile.path,
     configFile: false,

packages/remark-mdx/package.json

@@ -28,10 +28,10 @@
     "extract-imports-and-exports.js"
   ],
   "dependencies": {
-    "@babel/core": "7.6.0",
     "@babel/helper-plugin-utils": "7.0.0",
     "@babel/plugin-proposal-object-rest-spread": "7.5.5",
     "@babel/plugin-syntax-jsx": "7.2.0",
+    "@babel/standalone": "^7.5.5",
     "@mdx-js/util": "^1.4.5",
     "is-alphabetical": "1.0.3",
     "remark-parse": "7.0.1",

yarn.lock

@@ -1166,6 +1166,11 @@
   dependencies:
     regenerator-runtime "^0.12.0"
 
+"@babel/standalone@^7.5.5":
+  version "7.5.5"
+  resolved "https://registry.yarnpkg.com/@babel/standalone/-/standalone-7.5.5.tgz#9d3143f6078ff408db694a4254bd6f03c5c33962"
+  integrity sha512-YIp5taErC4uvp4d5urJtWMui3cpvZt83x57l4oVJNvFtDzumf3pMgRmoTSpGuEzh1yzo7jHhg3mbQmMhmKPbjA==
+
 "@babel/template@^7.0.0 <7.4.0":
   version "7.2.2"
   resolved "https://registry.yarnpkg.com/@babel/template/-/template-7.2.2.tgz#005b3fdf0ed96e88041330379e0da9a708eb2907"