fix "Error [ERR_REQUIRE_ESM]: require() of ES Module"

```
/home/runner/work/postcss-selector-prefix/postcss-selector-prefix/index.js:4
/home/runner/work/postcss-selector-prefix/postcss-selector-prefix/node_modules/escape-string-regexp/index.js
from
/home/runner/work/postcss-selector-prefix/postcss-selector-prefix/index.js
not supported.
/home/runner/work/postcss-selector-prefix/postcss-selector-prefix/node_modules/escape-string-regexp/index.js
in
/home/runner/work/postcss-selector-prefix/postcss-selector-prefix/index.js
to a dynamic import() which is available in all CommonJS modules.
(/home/runner/work/postcss-selector-prefix/postcss-selector-prefix/index.js:4:28)
(/home/runner/work/postcss-selector-prefix/postcss-selector-prefix/index.test.js:5:16)
{
```

index.js

@@ -1,13 +1,16 @@
 /**
  * @type {import('postcss').PluginCreator}
  */
-const escapeStringRegexp = require("escape-string-regexp");
+// escape function taken from
+// https://github.com/tc39/proposal-regex-escaping/blob/3d45b23af8e8824dd689deb35856a80fa52d78ca/polyfill.js
+const regExpEscape = (s) => String(s).replace(/[\\^$*+?.()|[\]{}]/g, "\\$&");
+
 module.exports = (prefix) => {
   return {
     postcssPlugin: "postcss-selector-prefix",
     Once(root) {
       // create prefix regex.
-      const escapedPrefix = escapeStringRegexp(prefix);
+      const escapedPrefix = regExpEscape(prefix);
       const re = new RegExp("^" + escapedPrefix);
 
       root.walkRules((rule) => {

package.json

@@ -27,8 +27,7 @@
     "node": ">=18.0.0"
   },
   "peerDependencies": {
-    "postcss": "^8.4.27",
-    "escape-string-regexp": "^5.0.0"
+    "postcss": "^8.4.27"
   },
   "devDependencies": {
     "eslint": "^8.47.0",