Add license & fix `long_description` in `setup.py`

[leofang]

Description

closes #2153

long_description is also fixed (with minimal effort in making README.md pretty) so as to pass twine check.

Checklist

• [ ] New or existing tests cover these changes.
• [ ] The documentation is up to date with these changes.

[leofang]

cc: @bryevdv @gevtushenko for vis

[github-actions[bot]]

🟩 CI finished in 10m 48s: Pass: 100%/1 | Total: 10m 48s | Avg: 10m 48s | Max: 10m 48s

• 🟩 pycuda: Pass: 100%/1 | Total: 10m 48s | Avg: 10m 48s | Max: 10m 48s

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👃 Inspect Changes

Modifications in project?

	Project
	CCCL Infrastructure
	libcu++
	CUB
	Thrust
	CUDA Experimental
+/-	pycuda

Modifications in project or dependencies?

	Project
	CCCL Infrastructure
	libcu++
	CUB
	Thrust
	CUDA Experimental
+/-	pycuda

🏃‍ Runner counts (total jobs: 1)

#	Runner
1	linux-amd64-gpu-v100-latest-1