Refactor health scan and introduce phpunit

Author: Gared

.gitignore

@@ -1,4 +1,5 @@
 composer.phar
+.phpunit.cache/
 
 .idea/
-vendor/
+vendor/

composer.json

@@ -7,6 +7,11 @@
       "Gared\\EtherScan\\": "src/"
     }
   },
+  "autoload-dev": {
+    "psr-4" : {
+      "Gared\\EtherScan\\Tests\\": "tests/"
+    }
+  },
   "require": {
     "php": ">=8.3",
     "ext-json": "*",
@@ -15,6 +20,7 @@
     "elephantio/elephant.io": "^4.8"
   },
   "require-dev": {
-    "phpstan/phpstan": "^2.0"
+    "phpstan/phpstan": "^2.0",
+    "phpunit/phpunit": "^12.5"
   }
 }