build

Add flake.nix and test on CI #68

Job	Run time
Haskell GHC 8.4.4 cabal	2m 21s
Generate GHC versions for nix flake build matrix	24s
Haskell GHC 8.6.5 cabal	2m 26s
Haskell GHC 8.8.4 cabal	2m 22s
Haskell GHC 8.10.7 cabal	2m 25s
Haskell GHC 9.0.2 cabal	2m 27s
Haskell GHC 9.2.2 cabal	2m 23s
Haskell GHC 9.4.2 cabal	2m 29s
Haskell GHC 9.6.6 cabal	2m 12s
Haskell GHC 9.8.1 cabal	2m 29s
Haskell GHC 9.10.1 cabal	1m 4s
Haskell GHC 9.12.1 cabal	45s
Nix Flake (ghc810, ubuntu-latest)	29s
Nix Flake (ghc810, macos-latest)	1m 19s
Nix Flake (ghc90, ubuntu-latest)	29s
Nix Flake (ghc90, macos-latest)	1m 20s
Nix Flake (ghc92, ubuntu-latest)	26s
Nix Flake (ghc92, macos-latest)	1m 29s
Nix Flake (ghc94, ubuntu-latest)	24s
Nix Flake (ghc94, macos-latest)	1m 3s
Nix Flake (ghc96, ubuntu-latest)	25s
Nix Flake (ghc96, macos-latest)	1m 2s
Nix Flake (ghc98, ubuntu-latest)	30s
Nix Flake (ghc98, macos-latest)	58s
Nix Flake (ghc910, ubuntu-latest)	31s
Nix Flake (ghc910, macos-latest)	1m 21s
Nix Flake (ghc912, ubuntu-latest)	30s
Nix Flake (ghc912, macos-latest)	1m 20s
	37m 23s

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