feat: add polyfill for RegExp.escape

the method is currently in ECMAScript standard draft 4 and not yet adopted
broadly enough. V8 has basic support, but I'm not betting on it coming soon, so
I've implemented a simple polyfill.

tsconfig.json

@@ -15,6 +15,7 @@
         "lib": ["esnext.weakref", "dom"]
     },
     "include": [
-        "src/**/*.ts"
+        "src/**/*.ts",
+        "src/types/**/*.d.ts"
     ]
 }