Add source urls to docker so tools can find sourcecode (#506)

For tools like renovate or dependabot, they like to put changelog notes in PRs updating deps. Having the labels allows the tools to link it back to sourcecode and share commits/release notes

Dockerfile

@@ -1,6 +1,6 @@
 # Builder
 FROM node:lts as builder
-
+LABEL org.opencontainers.image.url=https://github.com/Awesome-Technologies/synapse-admin org.opencontainers.image.source=https://github.com/Awesome-Technologies/synapse-admin
 ARG REACT_APP_SERVER
 
 WORKDIR /src