build

Add flake.nix and test on CI #73

Job	Run time
Check Flake	34s
Generate GHC versions for nix flake build matrix	25s
Haskell GHC 8.4.4 cabal	1m 40s
Haskell GHC 8.6.5 cabal	1m 49s
Haskell GHC 8.8.4 cabal	1m 41s
Haskell GHC 8.10.7 cabal	1m 40s
Haskell GHC 9.0.2 cabal	1m 43s
Haskell GHC 9.2.2 cabal	1m 48s
Haskell GHC 9.4.2 cabal	1m 53s
Haskell GHC 9.6.6 cabal	3m 12s
Haskell GHC 9.8.1 cabal	3m 34s
Haskell GHC 9.10.1 cabal	54s
Haskell GHC 9.12.1 cabal	42s
Nix Flake (ghc810, ubuntu-latest)	2m 15s
Nix Flake (ghc810, macos-latest)	34m 55s
Nix Flake (ghc90, ubuntu-latest)	2m 24s
Nix Flake (ghc90, macos-latest)	32m 6s
Nix Flake (ghc92, ubuntu-latest)	2m 23s
Nix Flake (ghc92, macos-latest)	24m 40s
Nix Flake (ghc94, ubuntu-latest)	2m 5s
Nix Flake (ghc94, macos-latest)	29m 39s
Nix Flake (ghc96, ubuntu-latest)	2m 20s
Nix Flake (ghc96, macos-latest)	5m 13s
Nix Flake (ghc98, ubuntu-latest)	2m 12s
Nix Flake (ghc98, macos-latest)	3m 48s
Nix Flake (ghc910, ubuntu-latest)	2m 5s
Nix Flake (ghc910, macos-latest)	3m 56s
	2h 51m 36s

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