update `.gitignore` file

[Tanryberdi]

We need to update .gitignore file for ignore all extension like .idea/ and etc...

[samjtro]

Merged via commit: 4576c3e

Thanks for the help! I had been putting that off, so I appreciate you stepping up to get that done. Let me know if you need anything for getting off the ground with go-tda.

Cheers!

[Tanryberdi]

I will investigate this repos, i will let you know if i have any questions