Add project files, gitignore etc

.gitignore

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+dist-newstyle/

README.md

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+# README
+
+* needs ghc-8.8.3 and cabal (use [ghcup](https://www.haskell.org/ghcup/) to install)
+* interval for the queue length can be adjusted: `holmusk-challenge --interval x.y`

cabal.project

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+packages: ./
+
+with-compiler: ghc-8.8.3

cabal.project.freeze

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+constraints: any.ansi-terminal ==0.10.3,
+             ansi-terminal -example,
+             any.ansi-wl-pprint ==0.6.9,
+             ansi-wl-pprint -example,
+             any.array ==0.5.4.0,
+             any.base ==4.13.0.0,
+             any.bytestring ==0.10.10.0,
+             any.colour ==2.3.5,
+             any.deepseq ==1.4.4.0,
+             any.directory ==1.3.6.0,
+             any.filepath ==1.4.2.1,
+             any.ghc-prim ==0.5.3,
+             any.integer-gmp ==1.0.2.0,
+             any.optparse-applicative ==0.15.1.0,
+             any.process ==1.6.8.0,
+             any.random ==1.1,
+             any.rts ==1.0,
+             any.time ==1.9.3,
+             any.transformers ==0.5.6.2,
+             any.transformers-compat ==0.6.5,
+             transformers-compat -five +five-three -four +generic-deriving +mtl -three -two,
+             any.unix ==2.7.2.2