gpu: nova-core: add initial documentation

Add the initial documentation of the Nova project.

The initial project documentation consists out of a brief introduction
of the project, as well as project guidelines both general and nova-core
specific and a task list for nova-core specifically.

The task list is divided into tasks for general Rust infrastructure
required by the project, tasks regarding GSP enablement and firmware
abstraction, general GPU driver tasks as well as tasks related to
external API design and test infrastructure.

Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Link: https://lore.kernel.org/r/20250306222336.23482-6-dakr@kernel.org


Signed-off-by: Danilo Krummrich <dakr@kernel.org>