Add JavaScript for Day 31 - Bubble Sort

[RrennM]

Please make sure you have done the following:

• [x] Created a folder with the name of language you code inside directory for the day you are making the contribution to
• [x] Added the source code file inside /Day<n>/<Language>/
• [x] Tested your code
• [x] Added credits (author and date) at the top of the code
• [x] Updated README.md for /Day <n>/
• [x] Added yourself as a contributor using all-contributors-cli