Fixed PHP deprecation (#47)

* Fixed PHP deprecation

* Update src/Issue/IssueCollection.php

Co-authored-by: Alexander M. Turek <[email protected]>

* Update src/Issue/IssueCollection.php

Co-authored-by: Alexander M. Turek <[email protected]>

Co-authored-by: Alexander M. Turek <[email protected]>

Author: Nyholm

src/Issue/IssueCollection.php

@@ -15,32 +15,32 @@ public function addIssue(Issue $issue)
         $this->issues[] = $issue;
     }
 
-    public function current()
+    public function current(): Issue
     {
         return $this->issues[$this->key];
     }
 
-    public function next()
+    public function next(): void
     {
         ++$this->key;
     }
 
-    public function key()
+    public function key(): int
     {
         return $this->key;
     }
 
-    public function valid()
+    public function valid(): bool
     {
         return isset($this->issues[$this->key()]);
     }
 
-    public function rewind()
+    public function rewind(): void
     {
         $this->key = 0;
     }
 
-    public function count()
+    public function count(): int
     {
         return count($this->issues);
     }