updated readme.

0x11-singly_linked_lists/README.md

@@ -1 +1,12 @@
-add contents here
+0x11-singly_linked_lists
+
+Table of contents:
+
+0-print_list.c   - prints each element of a list.
+1-list_len.c     - returns the length of the list.
+2-add_node.c     - adds node at the start of a list.
+3-add_node_end.c - adds node at the end of a list.
+4-free_list.c    - frees the list
+100-first.c      - executes a func before the main.
+lists.h          - lib for files.
+README.md        - me