Adds GH Actions to build the repo

This should use the repo and overlay tools to produce
a hackage overlay, automatically on push.

.github/workflows/publish.yml

@@ -5,10 +5,26 @@ on:
       - master
 jobs:
   Build-Overlay:
-    run-on: ubuntu-latest
+    runs-on: ubuntu-latest
     steps:
-      - name: Check out repository code
+      - name: Checkout 🛎️
         uses: actions/checkout@v2
-      - name: List files in the repository
-        run: |
-          ls -lah ${{ github.workspace }}
+      - uses: cachix/install-nix-action@v16
+        with:
+          nix_path: nixpkgs=channel:nixos-unstable
+      - name: Build 🔧
+        uses: workflow/nix-shell-action@v3
+        with:
+          packages: cabal-install, ghc, gnupg, unzip
+          script: |
+            mkdir $HOME/secrets
+            gpg --quiet --batch --yes --decrypt --passphrase="${{ secrets.KEYS_KEY }}" \
+              --output $HOME/secrets/keys.zip ${{ github.workspace }}/.github/keys.zip.gpg
+            unzip -qq $HOME/secrets/keys.zip
+            unzip -qq ${{ github.workspace }}/.github/pkg.zip
+            PATH=.:$PATH hackage-overlay-repo-tool --patches patches --keys keys/ build
+      - name: Deploy 🚀
+        uses: JamesIves/github-pages-deploy-action@v4.2.2
+        with:
+          branch: gh-pages # The branch the action should deploy to.
+          folder: build # The folder the action should deploy.

patches/foundation-0.0.26.1.patch

@@ -29,7 +29,7 @@ index 224c61308..ef25e37f8 100644
                        BangPatterns
                        DeriveDataTypeable
 
--  if impl(ghc < 8.0)
+-  if impl(ghc < 8.0) || impl(ghcjs)
 +  if impl(ghc < 8.0)
      buildable: False
    else