Added search in comments

app/Filter/TaskCommentFilter.php

@@ -0,0 +1,41 @@
+<?php
+
+namespace Kanboard\Filter;
+
+use Kanboard\Core\Filter\FilterInterface;
+use Kanboard\Model\Comment;
+use Kanboard\Model\Task;
+
+/**
+ * Filter tasks by comment
+ *
+ * @package filter
+ * @author  Frederic Guillot
+ */
+class TaskCommentFilter extends BaseFilter implements FilterInterface
+{
+    /**
+     * Get search attribute
+     *
+     * @access public
+     * @return string[]
+     */
+    public function getAttributes()
+    {
+        return array('comment');
+    }
+
+    /**
+     * Apply filter
+     *
+     * @access public
+     * @return FilterInterface
+     */
+    public function apply()
+    {
+        $this->query->ilike(Comment::TABLE.'.comment', '%'.$this->value.'%');
+        $this->query->join(Comment::TABLE, 'task_id', 'id', Task::TABLE);
+
+        return $this;
+    }
+}