Update docs/installation.rst

[jeongyoonlee]

Proposed changes

This PR fixes #666. It updates the installation instructions in docs/installation.rst with updates in #637. It also fixes the broken the download image in README.md and formatting warnings in docs/*.rst.

Types of changes

What types of changes does your code introduce to CausalML?
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• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation Update (if none of the other choices apply)

Checklist

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• I have read the CONTRIBUTING doc
• I have signed the CLA
• Lint and unit tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)
• Any dependent changes have been merged and published in downstream modules

Further comments

N/A

[vincewu51]

Hi Jeong, it seems some build has failed. Could you please rebase and re-run the build?

[jeongyoonlee]

Hi Jeong, it seems some build has failed. Could you please rebase and re-run the build?

Done!

[vincewu51]

668 is merged. Please rebase and it should solve the build failure.

[jeongyoonlee]

Done! Now all builds succeeded except PyPI installations, which we should separate and run only for new version releases.