added more ds and sorting algo

Merge pull request #2 from chandan-30/linked-list

reverse of linked list

Create doubly-linked-list.js

Make code clean

Added comments

Insert and delete methods

Used Node class for new node creations

append and prepend methods

Create linked-list-implementation.js

Merge pull request #1 from chandan-30/hash-table

Create hashtable-implementation.js

Create array-operations.js

Initial commit