Rename index.esm.js -> esm.mjs (#249 take 2) (#257)

* Rename index.esm.js -> esm.mjs
This is needed for node to properly deduce that the file is ESM.
Otherwise, node crashes when you try to `import("vectorious")` with an error like:
> Uncaught SyntaxError: Unexpected token 'export'

* 6.1.12

README.md

@@ -50,7 +50,7 @@ It exposes a global variable named `v` in the `window` object and can be accesse
 
 #### ES module
 
-Added in version 6.1.0, vectorious exposes an ES module bundle at `dist/index.esm.js` which can be imported using the `import` syntax:
+Added in version 6.1.0, vectorious exposes an ES module bundle at `dist/index.mjs` which can be imported using the `import` syntax:
 
 ```typescript
 import { array } from 'vectorious';

docs/vectorious/6.1.11/index.html

@@ -140,7 +140,7 @@ <h4>Browser</h4>
 &lt;/script>
 </code></pre>
 <h4>ES module</h4>
-<p>Added in version 6.1.0, vectorious exposes an ES module bundle at <code>dist/index.esm.js</code> which can be imported using the <code>import</code> syntax:</p>
+<p>Added in version 6.1.0, vectorious exposes an ES module bundle at <code>dist/index.mjs</code> which can be imported using the <code>import</code> syntax:</p>
 <pre class="prettyprint source lang-typescript"><code>import { array } from 'vectorious';
 
 const x = array([1, 2, 3]);

package.json

@@ -1,18 +1,18 @@
 {
   "name": "vectorious",
-  "version": "6.1.11",
+  "version": "6.1.12",
   "description": "A high performance linear algebra library.",
   "main": "dist/index.js",
   "browser": "dist/index.browser.js",
-  "module": "dist/index.esm.js",
+  "module": "dist/index.mjs",
   "types": "dist/index.d.ts",
   "files": [
     "dist"
   ],
   "exports": {
     ".": {
       "require": "./dist/index.js",
-      "import": "./dist/index.esm.js"
+      "import": "./dist/index.mjs"
     }
   },
   "scripts": {
@@ -21,7 +21,7 @@
     "docs": "tsc --outDir built && jsdoc --configure jsdoc.json && rimraf built",
     "build:node": "esbuild --bundle src/index.ts --minify --sourcemap --platform=node --outfile=dist/index.js --external:nblas --external:nlapack",
     "build:browser": "esbuild --bundle src/index.ts --minify --sourcemap --platform=browser --global-name=v --outfile=dist/index.browser.js --external:nblas --external:nlapack",
-    "build:esm": "esbuild --bundle src/index.ts --minify --sourcemap --format=esm --outfile=dist/index.esm.js --external:nblas --external:nlapack",
+    "build:esm": "esbuild --bundle src/index.ts --minify --sourcemap --format=esm --outfile=dist/index.mjs --external:nblas --external:nlapack",
     "build": "rimraf dist && tsc -emitDeclarationOnly && npm run build:node && npm run build:browser && npm run build:esm",
     "prepublishOnly": "npm run build"
   },