Embed README in index.rst

[anissa111]

Related to: https://github.com/NCAR/CUPiD/issues/38#issuecomment-1946567725

Summary of changes:

• fixes some small warnings/typos in README.md
• embeds README.md in docs/index.rst by copying CUPiD/README.md into the docs directory in docs/conf.py and removes the logo in the top header because having an image in the heading puts it in the sidebar toc tree, which looks really weird.
• Adds copied docs/README.md to the .gitignore because it should only be created/edited automatically during documentation generation and not actually committed to the repo
• Removes separate installation page for now, since the information is on the home page

See local results:

[TeaganKing]

Just to clarify, is the docs/README automatically generated and added to the documentation any time the normal README gets updated? If it's actually a copy that needs to be manually updated, maybe we could adjust that; if it's automatically maintained then I think this should be good to merge in...