add codetools for vignettes

[ben-schwen]

As shown by CI our images need codetools to build vignettes. Successful run with codetools is here

We could also add it to the docker images but it feels more right to do it here.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.97%. Comparing base (291a711) to head (0395e83).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #7542   +/-   ##
=======================================
  Coverage   98.97%   98.97%           
=======================================
  Files          87       87           
  Lines       16733    16733           
=======================================
  Hits        16561    16561           
  Misses        172      172           

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[github-actions]

No obvious timing issues in HEAD=CI_codetools

Generated via commit 0395e83

Download link for the artifact containing the test results: ↓ atime-results.zip

Task	Duration
R setup and installing dependencies	3 minutes and 5 seconds
Installing different package versions	22 seconds
Running and plotting the test cases	4 minutes and 3 seconds

[jangorecki]

Is the change of gitlab.io urls to lowercase required? Why?

[ben-schwen]

Is the change of gitlab.io urls to lowercase required? Why?

pkgdown gave me a warning about one of them and right now we use both, so a bit of consistency seemed right.

[aitap]

The dependency chain is litedown::fuse → xfun::record → xfun::find_locals -> codetools::findLocalsList. Arguably, litedown could depend on codetools, but this gets the job done as well.