CompatHelper: bump compat for Rasters to 0.8, (keep existing compat)

[github-actions]

This pull request changes the compat entry for the Rasters package from 0.4 to 0.4, 0.8.
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-commenter]

Codecov Report

Merging #82 (60210cf) into main (f0ab22b) will not change coverage.
The diff coverage is n/a.

❗ Current head 60210cf differs from pull request most recent head d5829b8. Consider uploading reports for the commit d5829b8 to get more accurate results

@@           Coverage Diff           @@
##             main      #82   +/-   ##
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  Coverage   96.96%   96.96%           
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  Files          16       16           
  Lines         363      363           
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  Hits          352      352           
  Misses         11       11