Automatically trim / from url, rm main.go from .gitignore

[erkexzcx]

This PR fixes this issue:

$ ./immich-go -server 'https://example.com/' -key xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx upload -google-photos /path/to/export/*.zip
immich-go  0.9.1, commit eb5078844270bab6e076931e8bec9b6fd070d725, built at 2023-12-13T17:58:58Z

PingServer, GET, https://example.com//api/server-info/ping, 200 OK
invalid character '<' looking for beginning of value
invalid character '<' looking for beginning of value

While 'https://example.com/' is giving above error, 'https://example.com' is working fine.

Currently, there is no error handling, but we don't need to - it's fine to automatically remove / from the end of -server value if it exists.

Also I've removed main.go from .gitignore as I assume it was added by accident? This fixes my recently raised #101.

[simulot]

Thanks for this PR