Add backend-specific dockerfiles, publish images

[gadomski]

Related Issue(s):

• Closes Dockerfile improvements, and and deployable version (comments and questions) #379
• Closes Put docker image on GHCR #485

Description:

Most of the changes to the main Dockerfile from #379 were implemented in #391. I think the remaining tasks were the deployable images for each backend. This PR adds those deployable images, some example docker-composes, and a section to the README.

Couple of notes:

• I also bumped the pgstac versions in CI to v0.6.13
• I moved the Dockerfiles to a docker/ folder, since the top-level was getting a little polluted w/ my two new Dockerfiles
• The package registry is currently set to private. Once this PR is approved, we should make it public
• I think my tagging should work as described in the README, but this could require a follow-up PR if I didn't get it quite right -- as always, testing CI-based stuff is a bit trial-and-error.
• These dockerfiles should be easily portable to the backend repos as a part of Split backends into independent repos #432, and that split will make the image tagging story much simpler

The backend-specific images are significantly smaller than the dev build:

PR Checklist:

• Code is formatted and linted (run pre-commit run --all-files)
• Tests pass (run make test)
• Documentation has been updated to reflect changes, if applicable, and docs build successfully (run make docs)
• Changes are added to the CHANGELOG.
• (once approved) Make the package registry public

[moradology]

Looks good. I don't think I have the permissions necessary to enable public container publishing. Reminder that this should be sorted out prior to merge

[gadomski]

Looks like it worked (from https://github.com/stac-utils/stac-fastapi/pkgs/container/stac-fastapi):