Add code linking to release posts

[chartgerink]

This PR adds automated code linking to the release posts.

I am more confident about this PR, as it builds on my last version #373, and simplifies the procedures. Specifically:

1. it only renders the new posts (not the entire posts/ folder)
2. renv testing was more reliable in terms of output
3. figured out that the dynamic creation of a code chunk that loads the library of the release was a big issue in the previous PR.

Probably a few other things. Ultimately, this is tested when it runs, and I will revisit this in day or two to see whether I have new insights.

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[Bisaloo]

You might still need to add downlit to renv.lock? Or is this handled by quarto?

[chartgerink]

Thanks for the review! 😊

Good question - I went back and double checked, as I could not remember exactly. Here is the log:

> renv::load()
- Project '~/git/epiverse-trace.github.io' loaded. [renv 1.1.2]
> renv::status()
No issues found -- the project is in a consistent state.
> install.packages('downlit')
The following package(s) will be installed:
- downlit [0.4.4]
These packages will be installed into "~/git/epiverse-trace.github.io/renv/library/macos/R-4.4/aarch64-apple-darwin24.2.0".

Do you want to proceed? [Y/n]: y

# Installing packages --------------------------------------------------------
- Installing downlit ...                        OK [linked from cache]
Successfully installed 1 package in 11 milliseconds.
> renv::status()
No issues found -- the project is in a consistent state.

From this, I would gather that the lockfile is okay. Do you have additional thoughts on this given this information? I keep missing minor details in renv so even a "seems okay" would help the confidence in merging this :)

[Bisaloo]

The code above only shows that downlit is not currently in renv.lock & that renv is not able to auto-detect if/that downlit is necessary, but it doesn't say if it should be there. This can typically happen for optional dependencies.

Given https://github.com/quarto-dev/quarto-cli/blob/a47d119b83895f5c036317c6c0885bb237e11df5/src/resources/rmd/rmd.R#L137-L140, I think it should be added.

renv doesn't use a completely airtight sandbox by default so it's possible that the system copy of downlit is still used in your local tests.