feat(reaction_contribution_dashboard): added small web app to explore reaction contributions over time

This is a static webpage which will view JSON files in a format which I use (and will build into GridFire) and let users investigate the contributions each reaction at each timestep makes to the overall abundance of each species. This is invaluable when debugging a newtowk

BREAKING CHANGE:

utils/app/reaction_contributions/Dockerfile

@@ -0,0 +1,5 @@
+FROM nginx:alpine
+
+COPY . /usr/share/nginx/html
+
+EXPOSE 80