fix phpstan errors, add it to ci

.github/workflows/formats.yml

@@ -39,3 +39,6 @@ jobs:
 
     - name: Coding Style Checks
       run: composer test:lint
+
+    - name: Type Checks
+      run: composer test:types

composer.json

@@ -39,6 +39,7 @@
         "test:unit": "pest --colors=always",
         "test": [
             "@test:lint",
+            "@test:types",
             "@test:unit"
         ]
     }

src/Contracts/Token.php

@@ -3,7 +3,6 @@
 namespace Felix\Sey\Contracts;
 
 use Felix\Sey\Runtime;
-use Felix\Sey\Tokens\NullToken;
 
 abstract class Token
 {

src/Runtime.php

@@ -36,9 +36,8 @@ public function __construct(string $expression, array $variables, array $functio
 
     public function run(): string
     {
-        while ($this->tokens->current() !== null) {
-            $this->tokens->current()->consume($this);
-            $this->tokens->next();
+        foreach ($this->tokens as $token) {
+            $token->consume($this);
         }
 
         // no more tokens to read but some operators are still in the stack

src/Tokens/Comma.php

@@ -10,7 +10,6 @@ class Comma extends Token
 {
     public function __construct(public string $value = ',')
     {
-
     }
 
     public function consume(Runtime $runtime): void