Bump versions, update renv.lock.

Adjust for breaking changes:
- Some obvious renames.
- Replace both `pivot_quantiles` and `unnest` `pivot_wider` patterns to
  `pivot_quantiles_wider`.
- Fix some `epi_recipe` and `frosting` printing that doesn't play well with
  knitr now.

Update _freeze files where a first pass visual diff identified
"real" differences rather than just a tiny visual offset.

A first pass visual diff did not identify any "real" differences with the
current versions, and suggests that some of these changes might just be a tiny
offset and/or size adjustment, but this would need a double check before trying
to avoid the updates to the _freeze & corresponding repo bloat.

* remove references to R6 and mutation
* use epiprocess correctly
* fix the authors section of DESCRIPTION
* upgrade renv
* update all packages in renv
* integrate Rprofile with user Rprofile

feat: update for epiprocess R6 refactor

* add a README file
* fix broken formatting in packages.bib
* get missing data for sliding-forecasters.qmd online
  instead of local files

Co-authored-by: Daniel McDonald <[email protected]>

Co-authored-by: Daniel McDonald <[email protected]>

fix: update tooling book