perf: ⚡️ dropping debug library to reduce bundle size

lib/client/utils.js

@@ -1,9 +1,16 @@
-const debug = require('debug');
-
 const PACKAGE_NAME = 'firstclasspostcodes';
 
 module.exports = {
-  debug: debug(PACKAGE_NAME),
+  debugging: false,
+
+  debug(message, ...args) {
+    if (this.debugging) {
+      const style = 'background: black; color: white;';
+      // eslint-disable-next-line no-console
+      console.log(`%c${PACKAGE_NAME}:%c ${message}`, style, 'inherit', ...args);
+    }
+    return this.debugging;
+  },
 
   on(eventName, handler) {
     const { $handlers = {} } = this;