fix!: output a single, cjs build

Supporting both cjs and esm is painful. esm is the future, but let's simplify
the EDS build for now, and then update to esm at some point in the future.

package.json

@@ -5,11 +5,9 @@
   "author": "CZI <[email protected]>",
   "homepage": "https://github.com/chanzuckerberg/edu-design-system",
   "license": "MIT",
+  "type": "commonjs",
   "exports": {
-    ".": {
-      "import": "./lib/index.js",
-      "require": "./lib/index.cjs"
-    },
+    ".": "./lib/index.js",
     "./index.css": "./lib/index.css",
     "./fonts.css": "./lib/tokens/fonts.css",
     "./tailwind.config": "./tailwind.config.ts"

rollup.config.mjs

@@ -7,24 +7,14 @@ import postcss from 'rollup-plugin-postcss';
  */
 export default {
   input: 'src/index.ts',
-  output: [
-    {
-      dir: 'lib',
-      format: 'es',
-      preserveModules: true,
-      preserveModulesRoot: 'src',
-      sourcemap: true,
-    },
-    {
-      dir: 'lib',
-      format: 'cjs',
-      preserveModules: true,
-      preserveModulesRoot: 'src',
-      sourcemap: true,
-      entryFileNames: '[name].cjs',
-      interop: 'auto',
-    },
-  ],
+  output: {
+    dir: 'lib',
+    format: 'cjs',
+    preserveModules: true,
+    preserveModulesRoot: 'src',
+    sourcemap: true,
+    interop: 'auto',
+  },
   /**
    * With the nodeResolve plugin, this marks all EDS node_modules as external, aka provided by the consumer.
    * Since EDS is not imported directly into a web <script>, package managers (such as npm or yarn)