Add symlinks to publish readme to pypi

[jonhealy1]

Related Issue(s):

• None

Description:

Add symlinks from project-specific readme files to main readme. This will improve the pypi release page. https://pypi.org/project/stac-fastapi.elasticsearch/

PR Checklist:

• [x] Code is formatted and linted (run pre-commit run --all-files)
• [x] Tests pass (run make test)
• [x] Documentation has been updated to reflect changes, if applicable
• [x] Changes are added to the changelog