Add docs

[hdrake]

This pull request introduces comprehensive improvements to the documentation and packaging for the sectionate project. The changes focus on enhancing installation instructions, updating badges, adding Conda packaging, and establishing a robust Sphinx documentation setup.

Documentation and Installation Improvements:

• Updated the README.md to feature new badges for PyPI, Conda, documentation, and license, and revised installation instructions to recommend Conda as the default method.
• Added a new docs/source/installation.rst with detailed requirements and multiple installation methods, including Conda, Pip, and GitHub.
• Created a new docs/source/index.rst to serve as the main entry point for Sphinx documentation, including a table of contents linking to installation and example notebooks.

Conda Packaging:

• Introduced a conda/meta.yaml recipe for packaging, specifying dependencies, build instructions, test commands, and metadata for Conda Forge distribution.
• Updated ci/environment.yml to add the nodefaults channel, ensuring only conda-forge packages are used.

Sphinx Documentation Setup:

• Added a Sphinx Makefile and Windows batch file for building documentation, along with a custom responsive CSS for improved layout. [1] [2] [3]
• Created a new docs/source/conf.py with configuration for project metadata, notebook copying automation, theme customization, and extension setup.
• Updated docs/environment.yml to include Sphinx, nbsphinx, ipykernel, and pip for documentation builds.