My Dockerfiles for Tahoe-LAFS

This adds two Dockerfiles for Tahoe-LAFS, usable from a Tahoe-LAFS checkout:

One 'base' file which is quite short and sweet, but results in a big OCI image. It's almost identical to the 'base' Dockerfile that recently was removed from Tahoe-LAFS (in commit 0e4d39229ace8ec82f2a4598dbcee619fa4fa408). It's nice to build on and to play around with Tahoe-LAFS.

The second Dockerfile, Dockerfile-distroless, is a two-stage builder which takes above Dockerfile, clears out the .git index and creates a rather minimal Distroless OCI image from it. It has a Python interpreter, Tahoe-LAFS and its dependencies, not much else (not even a busybox shell). This is what I would deploy to a cloud container runtime (such as Kubernetes, Google Cloud Run, AWS ECS, etc). Both are not heavily tested, I consider them experimental.