This PR implements the code for exponential search in javascript referred in issue #42.

[Ankitasareen]

This PR implements the code for in referred in issue #

I have read the contributing guidelines in CONTRIBUTING.md and have ensured the following:

• [x] My code is placed in the required directory as outlined in CONTRIBUTING.md
• [ ] My code file is named according to CONTRIBUTING.md
• [ ] Variables, classes, functions etc. follow camel case as outlined in CONTRIBUTING.md
• [ ] My code hasn't been implemented or claimed by someone else and I have checked the present issues and PRs for the same
• [ ] My code is well commented
• [ ] If my code is the first implementation of , I have added the link to this directory in README.md
• [x] I have not copied my code from anywhere

This PR creates/modifies the README for

I have read the contributing guidelines in CONTRIBUTING.md and have ensured the following:

• [ ] Algo name (as heading)
• [ ] A small description about algo
• [ ] Time Complexity (Worst, Average, Best case)
• [ ] Space Complexity (Worst, Average, Best case)
• [ ] Logic and Pseudocode
• [ ] Instructions for running code