CompatHelper: bump compat for "Documenter" to "0.27" for package docs

[github-actions]

This pull request changes the compat entry for the Documenter package from 0.26 to 0.26, 0.27 for package docs.

This keeps the compat entries for earlier versions.

Note: I have not tested your package with this new compat entry. It is your responsibility to make sure that your package tests pass before you merge this pull request.

[codecov]

Codecov Report

Merging #10 (03c9317) into main (c5e42a3) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##              main       #10   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            4         4           
  Lines           91        91           
=========================================
  Hits            91        91           

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