Fix missing CVAT_BASE_URL env

[Marishka17]

Motivation and context

How has this been tested?

Checklist

• I submit my changes into the develop branch
• I have added a description of my changes into the CHANGELOG file
  - [ ] I have updated the documentation accordingly
  - [ ] I have added tests to cover my changes
  - [ ] I have linked related issues (see GitHub docs)
  - [ ] I have increased versions of npm packages if it is necessary
  (cvat-canvas,
  cvat-core,
  cvat-data and
  cvat-ui)

License

• I submit my code changes under the same MIT License that covers the project.
  Feel free to contact the maintainers if that's a concern.

[arshanskiyav]

@Marishka17, how should I use this env?
export CVAT_HOST=my_domain.me

I added CVAT_BASE_URL: http://${CVAT_HOST:-localhost}:8080/new_cvat to my docker-compose.yml
and expect my cvat instance to be available at http://my_domain.me:8080/new_cvat/tasks?page=1 or http://localhost:8080/new_cvat/tasks?page=1
but the URL in the address bar has not changed (http://my_domain.me/tasks?page=1 )

thanks