feat: add git-lfs to Docker images

This change adds support for git large files storage (lfs) by adding the
`git-lfs` package to both the default and `slim` Docker images. This
change was prompted by a user request and barely increases the
uncompressed image size. The feature will be useful for anyone making
use of git lfs in the repositories they wish to analyze with Phylum.

Dockerfile

@@ -210,6 +210,7 @@ RUN \
     apt-get upgrade --yes; \
     apt-get install --yes --no-install-recommends \
         git \
+        git-lfs \
         bundler \
         maven \
         procps \

Dockerfile.slim

@@ -180,7 +180,7 @@ RUN set -eux; \
     # Install prerequisites
     apt-get update; \
     apt-get upgrade --yes; \
-    apt-get install --yes --no-install-recommends git procps binutils; \
+    apt-get install --yes --no-install-recommends git git-lfs procps binutils; \
     # Make ENTRYPOINT alternative script available
     chmod +x "${PHYLUM_VENV}/bin/entrypoint.sh"; \
     # Install Phylum CLI