fix(deps): require PHP 8.1 or higher (#15)

8.1 is the minimum version with Security Support: https://www.php.net/supported-versions.php

Author: jradcliff

google-analytics-admin/composer.json

@@ -1,5 +1,6 @@
 {
  "require": {
+ "php": ">=8.1",
  "google/analytics-admin": "^0.26.0"
  },
  "require-dev": {

google-analytics-data/composer.json

@@ -1,5 +1,6 @@
 {
  "require": {
+ "php": ">=8.1",
  "google/analytics-data": "^0.22.0"
  },
  "require-dev": {