added testing for Concerts.html

[KenichiroAnderson]

you will need jest in your vscode to run these tests but they do work and do create false concerts and artists and ensure that they are working. so this one is ready for push to main

[KenichiroAnderson]

sorry, i originally made this in main then realized that I cant do that, got to follow protocol

[EricSmith10]

thanks for making the tests Ken, looks good. Good comments as well

[NathanIsCoding]

Looks good, tests seem reasonable and code is clear.

[KevinKim99]

testing cases are well functioning, code is well written in neat way