add egison
add egison

Checklist:
- [x] Meaningful commit message, eg `add my-cool-package` (please not mention `build-constraints.yml`)
- [x] At least 30 minutes have passed since uploading to Hackage
- [x] On your own machine, in a _new directory_, you have successfully run the following set of commands (replace `$package` with the name of the package that is submitted, and `$version` with the version of the package you want to get into Stackage):

      stack unpack $package-$version  # $version is optional
      stack init --resolver nightly
      stack build --resolver nightly --haddock --test --bench --no-run-benchmarks
iand675/stackage,michalkonecny/stackage,mrkkrp/stackage,spencerjanssen/stackage,soenkehahn/stackage,stackbuilders/stackage,jonschoning/stackage,asr/stackage,athanclark/stackage,massysett/stackage,simonmichael/stackage,fimad/stackage,fpco/stackage,Daniel-Diaz/stackage,clinty/stackage