Fix docker build

**Description:**

refreshed my fork with upstream, docker wasn't building anymore, added the file that was missing as a "cargo cult" solution

**TestPlan:**

run the docker build, now the web container starts correctly

docker/Dockerfile

@@ -37,4 +37,7 @@ WORKDIR /explain
 
 COPY docker/explain.json explain.pl ./
 
+RUN mkdir -p /explain/log/
+RUN touch /explain/log/development.log
+
 ENTRYPOINT /explain/explain.pl daemon