Gray Paper Reader future

While Gray Paper ossifies some of the features in the reader might become less useful over time. However the tool can become a paper-based knowledge base via #83 #144

The ideas that are worth to explore:
1. Annotations containing links to external documentation (for instance https://docs.jamcha.in/) - a "specification-centric" view that allows you to go into implementation details easily.
2. Annotations containing links to implementation(s) source code (e.g. github) - explore the specification and see how things are implemented in different languages (related: #145)
3. Links to presentations about particular sections (for instance JAM lectures: https://www.youtube.com/watch?v=wbnTnBQNDr4&list=PLwcnAOKMj-Ab7sDej2P4peqGxu2mTGYNy )