Fix masterminds-html5 lib php8-1 notice return type use phpstan

src/HTML5/Parser/StringInputStream.php

@@ -177,7 +177,7 @@ public function getColumnOffset()
      *
      * @return string The current character.
      */
-    public function current()
+    public function current(): mixed
     {
         return $this->data[$this->char];
     }
@@ -186,15 +186,15 @@ public function current()
      * Advance the pointer.
      * This is part of the Iterator interface.
      */
-    public function next()
+    public function next(): void
     {
         $this->char ++;
     }
 
     /**
      * Rewind to the start of the string.
      */
-    public function rewind()
+    public function rewind(): void
     {
         $this->char = 0;
     }
@@ -204,7 +204,7 @@ public function rewind()
      *
      * @return bool Is the current pointer location valid.
      */
-    public function valid()
+    public function valid(): bool
     {
         if ($this->char < $this->EOF) {
             return true;
@@ -324,7 +324,7 @@ public function peek()
         return false;
     }
 
-    public function key()
+    public function key(): int
     {
         return $this->char;
     }