feat: add Docker image (Linux x64)

[reneleonhardt]

• Rootless Docker image (not multi-arch)
• Allow Dependabot to update Docker and GitHub Actions

This image is not yet integrated into the build / release workflow, it serves as an example how easily users could integrate it into their own Docker workflows / builds:

COPY --from=evanwallace/esbuild /bin/esbuild /bin/
RUN /bin/esbuild

Or locally instead of installing / updating a binary package:

docker run --rm -it evanwallace/esbuild --help