Automatically ignore trailling slash for BACKEND_ENDPOINT

[Tchoupinax]

Hey,

In the documentation there is an env var to change the backend endpoint.

BACKEND_ENDPOINT="http://my-custom-domain.com" helm-viewer my-chart --push

If you put a / at the end of the URL, it causes an issue (because the url contains two slash). It should ignore the additional slash.

[Tchoupinax]

Fixed