Add Abstract FFT compat

[DhairyaLGandhi]

No description provided.

[DilumAluthge]

@DhairyaLGandhi If you haven't done so already, you should probably make a similar PR to GPUArrays.jl.

[maleadt]

It's always good to bump the package in the Manifest too so that the CI run is meaningful.

[codecov]

Codecov Report

Merging #721 (49a5cd1) into compat (02ac36a) will decrease coverage by 0.15%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           compat     #721      +/-   ##
==========================================
- Coverage   77.27%   77.12%   -0.16%     
==========================================
  Files         116      116              
  Lines        6438     6438              
==========================================
- Hits         4975     4965      -10     
- Misses       1463     1473      +10     

Impacted Files	Coverage Δ
lib/library_types.jl	18.18% <0.00%> (-8.09%)	⬇️
src/utilities.jl	90.16% <0.00%> (-1.64%)	⬇️
lib/cublas/wrappers.jl	90.57% <0.00%> (-0.43%)	⬇️
src/pool.jl	72.50% <0.00%> (+0.83%)	⬆️

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