feat: conditionally export ECMAScript modules (#3377)

* feat: conditionally export ECMAScript modules

BREAKING CHANGE: With module loaders that support conditional exports
and ECMAScript modules, `import katex from 'katex';` will import the
ECMAScript module.

You can now use:
|Before                                    |After                             |
|------------------------------------------|----------------------------------|
|`require('katex/dist/contrib/[name].js')` | `require('katex/contrib/[name]')`|
|`import katex from 'katex/dist/katex.mjs'`| `import katex from 'katex'`      |
|`import 'katex/dist/contrib/[name].mjs'`  | `import 'katex/contrib/[name]'`  |

docs/migration.md

@@ -3,27 +3,38 @@ id: migration
 title: Migration Guide
 ---
 
-As of KaTeX 1.0, we've changed how MacroExpander and Parser work in order to close
-some gaps between KaTeX and LaTeX and therefore there may be breaking changes.
+## v0.14.0
 
-## Macro arguments
+With module loaders that support conditional exports and ECMAScript modules,
+`import katex from 'katex';` will import the ECMAScript module.
+
+You can now use:
+|Before                                    |After                             |
+|------------------------------------------|----------------------------------|
+|`require('katex/dist/contrib/[name].js')` | `require('katex/contrib/[name]')`|
+|`import katex from 'katex/dist/katex.mjs'`| `import katex from 'katex'`      |
+|`import 'katex/dist/contrib/[name].mjs'`  | `import 'katex/contrib/[name]'`  |
+
+## v0.13.0
+
+### Macro arguments
 Tokens will not be expanded while parsing a macro argument. For example, `\frac\foo\foo`,
 where the `\foo` is defined as `12`, will be parsed as `\frac{12}{12}`, not
 `\frac{1}{2}12`. To expand the argument before parsing, `\expandafter` can
 be used like `\expandafter\frac\foo\foo`.
 
-## `\def`
+### `\def`
 `\def` no longer accepts a control sequence enclosed in braces. For example,
 `\def{\foo}{}` no longer works and should be changed to `\def\foo{}`.
 
 It also no longer accepts replacement text not enclosed in braces. For example,
 `\def\foo1` no longer works and should be changed to `\def\foo{1}`.
 
-## `\newline` and `\cr`
+### `\newline` and `\cr`
 `\newline` and `\cr` no longer takes an optional size argument. To specify vertical
 spacing, `\\` should be used.
 
-## `\cfrac`, `\color`, `\textcolor`, `\colorbox`, `\fcolorbox`
+### `\cfrac`, `\color`, `\textcolor`, `\colorbox`, `\fcolorbox`
 They are no longer allowed as an argument to primitive commands, such as `\sqrt`
 (without the optional argument) and super/subscript. For example,
 `\sqrt\textcolor{red}{x}` no longer works and should be changed to

docs/node.md

@@ -63,17 +63,11 @@ KaTeX is exported as a CommonJS module, which can be imported using `require`:
 const katex = require('katex');
 ```
 
-If you're using a module loader, transpiler, or bundler that supports interoperability
-between ECMAScript module and CommonJS module, you can use `import`:
+KaTeX also conditionally exports an ECMAScript module:
 ```js
 import katex from 'katex';
 ```
 
-KaTeX also provides an ECMAScript module:
-```js
-import katex from 'katex/dist/katex.mjs'
-```
-
 > The ES module contains ES6 syntaxes and features, and may need transpiling to
 use in old environments.
 
@@ -94,6 +88,6 @@ mhchem in Node as follows:
 
 ```js
 const katex = require('katex');
-require('katex/dist/contrib/mhchem.js'); // modify katex module
+require('katex/contrib/mhchem'); // modify katex module
 const html = katex.renderToString('\\ce{CO2 + C -> 2 C0}');
 ```

package.json

@@ -3,6 +3,33 @@
   "version": "0.13.24",
   "description": "Fast math typesetting for the web.",
   "main": "dist/katex.js",
+  "exports": {
+    ".": {
+      "require": "./dist/katex.js",
+      "import": "./dist/katex.mjs"
+    },
+    "./contrib/auto-render": {
+      "require": "./dist/contrib/auto-render.js",
+      "import": "./dist/contrib/auto-render.mjs"
+    },
+    "./contrib/mhchem": {
+      "require": "./dist/contrib/mhchem.js",
+      "import": "./dist/contrib/mhchem.mjs"
+    },
+    "./contrib/copy-tex": {
+      "require": "./dist/contrib/copy-tex.js",
+      "import": "./dist/contrib/copy-tex.mjs"
+    },
+    "./contrib/mathtex-script-type": {
+      "require": "./dist/contrib/mathtex-script-type.js",
+      "import": "./dist/contrib/mathtex-script-type.mjs"
+    },
+    "./contrib/render-a11y-string": {
+      "require": "./dist/contrib/render-a11y-string.js",
+      "import": "./dist/contrib/render-a11y-string.mjs"
+    },
+    "./*": "./*"
+  },
   "homepage": "https://katex.org",
   "repository": {
     "type": "git",