Integrate H5 cluster estimate into MCMC howto

[joshwlambert]

• Please check if the PR fulfills these requirements

• I have read the CONTRIBUTING guidelines
• A new item has been added to NEWS.md
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)
• Checks have been run locally and pass

• What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)

This PR integrates the H5 R and k estimation using MCMC currently on the h5_example branch into the reproduction_number_cluster_size.qmd howto (see #107). It uses tabs to separate the two examples.

• Does this PR introduce a breaking change? (What changes might users need to make in their application due to this PR?)

No

• Questions:

• @adamkucharski what is the source of the H5 cluster size data? I haven't referenced it in the Steps in detail section.

[joshwlambert]

The GHA for this PR is currently failing due to Error installing package 'matrixStats'. I haven't changed the renv.lock file in this PR so this is likely a wider issue in howto.