CompatHelper: bump compat for Rasters to 0.9, (keep existing compat)

[github-actions]

This pull request changes the compat entry for the Rasters package from 0.4, 0.8 to 0.4, 0.8, 0.9.
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 #95 (961d042) into main (21b8561) will increase coverage by 1.15%.
The diff coverage is n/a.

❗ Current head 961d042 differs from pull request most recent head 9fc1a25. Consider uploading reports for the commit 9fc1a25 to get more accurate results

@@            Coverage Diff             @@
##             main      #95      +/-   ##
==========================================
+ Coverage   95.65%   96.81%   +1.15%     
==========================================
  Files          14       14              
  Lines         345      345              
==========================================
+ Hits          330      334       +4     
+ Misses         15       11       -4     

see 1 file with indirect coverage changes