Display version differences and summary

[tomusdrw]

It should be possible to see differences between two versions and we can also use an LLM to generate a summary.

[tomusdrw]

The mechanism of #83 should be used to display the differences

[tomusdrw]

Example what this could look like: https://github.com/FluffyLabs/graypaper-notes/blob/gh-pages/version-0.5.4.json

Ideally the process would be automated and would be using github commits as the source of description of the changes. LLM could be used on top to summarize the PR description or changes in the prose.