[RootlessDocker] Set correct group permissions in Dockerfile to allow users to be added to group

[aravindev]

This pull request introduces a permissions update in the Docker build process to improve collaboration for users in the isaac-sim group. The main change ensures that all users in the group can create, modify, or execute files within the /isaac-sim and /tmp directories.

Permissions and collaboration:

• Added a chmod -R g+wsx /isaac-sim /tmp command to grant group write and execute permissions, facilitating shared access for all users in the isaac-sim group.

@sheikh-nv It would be nice if this change could be incoorporated into the Dockerfile such that downstream rootless docker images can create users that mirror local user permissions and work seamlessly.

Currently, adding a new user to the isaac-sim group does not provide necessary privileges, which is limiting.