Run browsertrix in docker on the host

Install docker in the container

Add a named volume called `browsertrix`

Mount the named volume in the worker at /crawls

Expose the host docker socket

Override the environment variable from auto-archiver's Dockerfile so
that it will call docker.

This will require setting new configs in orchestration.yaml:

 wacz_archiver_enricher:
  browsertrix_home: auto-archiver-api_browsertrix
  wacz_collections: /crawls

src/Dockerfile

@@ -4,6 +4,8 @@ FROM bellingcat/auto-archiver
 # set work directory
 WORKDIR /app
 
+RUN curl -fsSL https://get.docker.com -o get-docker.sh && \
+    sh get-docker.sh
 # set environment variables
 ENV PYTHONUNBUFFERED 1
 ENV PYTHONDONTWRITEBYTECODE 1