Request Conda support

### Checklist

- [X] I have searched for [similar issues](https://github.com/isl-org/Open3D/issues).
- [X] For Python issues, I have tested with the [latest development wheel](http://www.open3d.org/docs/latest/getting_started.html#development-version-pip).
- [X] I have checked the [release documentation](http://www.open3d.org/docs/release/) and the [latest documentation](http://www.open3d.org/docs/latest/) (for `master` branch).

### Proposed new feature or change

Support conda installation of `open3d` in order to better integrate with the broader python ecosystem.

### References

Conda is the preferred package and environment manager for a significant portion of the python community. When working on a project using conda, it is best to install all packages via conda and only use pip if absolutely necessary in order to ensure the best environment resolution. Mixing the two can lead to package conflicts and unsolvable environments.

https://docs.conda.io/projects/conda/en/latest/user-guide/tasks/manage-pkgs.html#:~:text=You%20can%20install%20pip%20in,current%20conda%20environment%20is%20used.

### Additional information

I tried using the below conda package, but was disappointed to see the deprecation warning
```text
Warning] Since Open3D 0.15, installing Open3D via conda is deprecated. Please re-install Open3D via: `pip install open3d -U`.
```

https://anaconda.org/open3d-admin/open3d