Pip install instructions in docs, pyproject.toml changes to get nvMolKit's pypi page pretty

[scal444]

Also includes a few env-var and dependency things that are used in a downstream PR for automating the pip build better.

[greptile-apps]

Greptile Summary

This PR adds pip installation documentation to both README.md and docs/index.rst, and enriches pyproject.toml with metadata (inline readme, license, authors, keywords, classifiers, project URLs) to improve the nvMolKit PyPI page appearance. A handful of build env vars (CMAKE_BUILD_PARALLEL_LEVEL, MAKEFLAGS, CONAN_CPU_COUNT) are added to environment-pass to support downstream build automation.

• Docs: Both README.md and docs/index.rst now explain the standard pip install nvmolkit path and the per-RDKit-version pinned variant hosted on GitHub Pages.
• pyproject.toml: Adds a rich inline readme block, SPDX license string, author info, keyword list, Python/topic classifiers, and canonical project URLs; no functional logic changes.

Confidence Score: 5/5

Documentation-only and metadata changes with no functional code modifications; safe to merge.

All changes are limited to documentation prose and PyPI metadata fields. No functional logic, build scripts, or library code is altered. The environment-pass addition is a straightforward passthrough of standard build-parallelization variables.

No files require special attention.

Important Files Changed

Filename	Overview
README.md	Adds pip installation section with standard and RDKit-pinned variant instructions
docs/index.rst	Mirrors the pip installation instructions from README into the RST documentation
pyproject.toml	Enriches PyPI metadata (description, readme, license, authors, keywords, classifiers, URLs) and extends environment-pass for build parallelization

_{Reviews (4): Last reviewed commit: "Undo broken python dep" | Re-trigger Greptile}

[evasnow1992]

Changes look good to me. Thanks!