build

Add flake.nix and test on CI #72

Job	Run time
Generate GHC versions for nix flake build matrix	20s
Check Flake	37s
Haskell GHC 8.4.4 cabal	2m 35s
Haskell GHC 8.6.5 cabal	2m 47s
Haskell GHC 8.8.4 cabal	2m 40s
Haskell GHC 8.10.7 cabal	2m 46s
Haskell GHC 9.0.2 cabal	1m 42s
Haskell GHC 9.2.2 cabal	1m 44s
Haskell GHC 9.4.2 cabal	1m 55s
Haskell GHC 9.6.6 cabal	3m 14s
Haskell GHC 9.8.1 cabal	3m 34s
Haskell GHC 9.10.1 cabal	1m 42s
Haskell GHC 9.12.1 cabal	1m 50s
Nix Flake (ghc810, ubuntu-latest)	2m 3s
Nix Flake (ghc810, macos-latest)	25m 33s
Nix Flake (ghc90, ubuntu-latest)	3m 33s
Nix Flake (ghc90, macos-latest)	21m 47s
Nix Flake (ghc92, ubuntu-latest)	2m 9s
Nix Flake (ghc92, macos-latest)	21m 9s
Nix Flake (ghc94, ubuntu-latest)	2m 9s
Nix Flake (ghc94, macos-latest)	25m 45s
Nix Flake (ghc96, ubuntu-latest)	2m 7s
Nix Flake (ghc96, macos-latest)	3m 20s
Nix Flake (ghc98, ubuntu-latest)	2m 10s
Nix Flake (ghc98, macos-latest)	3m 5s
Nix Flake (ghc910, ubuntu-latest)	2m 9s
Nix Flake (ghc910, macos-latest)	4m 51s
	2h 29m 16s

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