Implement two types of q_insert functions

Implement the following insert functions:
- q_insert_head(): Insert an element at the head of the queue
- q_insert_tail(): Insert an element at the tail of the queue

queue.c

@@ -28,12 +28,40 @@ void q_free(struct list_head *head) {}
 /* Insert an element at head of queue */
 bool q_insert_head(struct list_head *head, char *s)
 {
+    if (!head)
+        return false;
+
+    element_t *new_element = malloc(sizeof(element_t));
+    if (!new_element)
+        return false;
+
+    new_element->value = strdup(s);
+    if (!new_element->value) {
+        free(new_element);
+        return false;
+    }
+
+    list_add(&new_element->list, head);
     return true;
 }
 
 /* Insert an element at tail of queue */
 bool q_insert_tail(struct list_head *head, char *s)
 {
+    if (!head)
+        return false;
+
+    element_t *new_element = malloc(sizeof(element_t));
+    if (!new_element)
+        return false;
+
+    new_element->value = strdup(s);
+    if (!new_element->value) {
+        free(new_element);
+        return false;
+    }
+
+    list_add_tail(&new_element->list, head);
     return true;
 }