feat(ci): add some actions

.github/workflows/build.yml

@@ -0,0 +1,19 @@
+name: Build
+
+on:
+  push:
+    branches: [ main ]
+  pull_request:
+    branches: [ main ]
+
+jobs:
+  build:
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        os: [ubuntu-latest, macos-latest]
+    steps:
+    - uses: actions/checkout@v3
+    - uses: DeterminateSystems/nix-installer-action@main
+    - uses: DeterminateSystems/magic-nix-cache-action@main
+    - run: nix build .#mugraph-node

.github/workflows/notes.yml

@@ -0,0 +1,22 @@
+# Uses git-gloss to generate notes to commits related to a pull request
+name: Push notes (using git-gloss)
+on:
+  push:
+    branches:
+      - main
+permissions:
+  contents: write
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - uses: fregante/setup-git-user@v2
+      - run: |
+          git fetch origin "refs/notes/*:refs/notes/*"
+          curl -fsSLO \
+              https://sideshowbarker.github.io/git-gloss/git-gloss \
+              && bash ./git-gloss
+          git push origin "refs/notes/*"
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}