Enable usage of this plugin by release-it's require based system

Since the move to `type: modules` in package.json this package no longer
works within `release-it`'s normal plugin resolution / resolving steps
(because it is internally using `import-from` which is basically just
doing `require` relative to the current working directory; and you can't
`require` a ES modules based file).

This adds a very simple wrapper script and leverages the pre-existing
static async method `isEnabled` on the plugin instance to absorb async
from a dynamic `import()` expression. The `PluginClass.isEnabled()` hook
is always called before `new PluginClass` is called, so this system of
absorbing the async in `isEnabled` then returning an instance of "the
real plugin" from the fake plugin's constructor is pretty safe.

cjs-wrapper.cjs

@@ -0,0 +1,17 @@
+// this will be populated inside the static `isEnabled` method just below
+let RealPlugin;
+
+module.exports = class FakeCJSWrapperPlugin {
+
+  static async isEnabled() {
+    // we use the async of this method to enable us to absorb the dynamic
+    // import statement
+    let RealPluginModule = await import('./index.js');
+    RealPlugin = RealPluginModule.default;
+  }
+
+  constructor(...args) {
+    // now we just use the "real plugin" as is
+    return new RealPlugin(...args);
+  }
+}

package.json

@@ -43,6 +43,12 @@
     "release-it": "^14.11.6",
     "sinon": "^11.1.2"
   },
+  "exports": {
+    ".": {
+      "import": "./index.js",
+      "require": "./cjs-wrapper.cjs"
+    }
+  },
   "peerDependencies": {
     "release-it": "^14.0.0"
   },
@@ -54,7 +60,7 @@
   },
   "release-it": {
     "plugins": {
-      "./index.js": {
+      "./cjs-wrapper.cjs": {
         "infile": "CHANGELOG.md",
         "launchEditor": true
       }