Add a Dockerfile which builds a site-generator app

This builds the container with the needed Perl modules, templates,
and a default configuration file.

Dockerfile

@@ -0,0 +1,24 @@
+FROM perl:stable
+
+RUN cpan cpanm Config::Std \
+   && cpanm Template \
+   && cpanm Template::Plugin::DBI \
+   && cpanm Template::Plugin::HTML::Strip \
+   && cpanm DBD::SQLite \
+   && cpanm Tie::DBI \
+   && cpanm Date::Calc \
+   && cpanm Text::CSV_XS \
+   && cpanm HTML::Entities \
+   && mkdir -p /usr/src/app
+
+WORKDIR /usr/src/app
+
+ADD site-generator /usr/src/app/site-generator
+ADD site.cfg /usr/src/app/site.cfg
+ADD templates /usr/src/app/templates
+ADD LICENSE /usr/src/app/LICENSE
+
+# Tell Perl where to find the local modules
+ENV PERL5LIB=/usr/local/lib/perl5/site_perl
+
+ENTRYPOINT ["/usr/src/app/site-generator"]