Install Sass differently

Otherwise, we run into parcel-bundler/watcher#152

.github/workflows/build.yml

@@ -45,9 +45,7 @@ jobs:
           ghcup config add-release-channel https://raw.githubusercontent.com/haskell/ghcup-metadata/develop/ghcup-cross-0.0.8.yaml
           ghcup install ghc --set wasm32-wasi-9.10.1 -- $CONFIGURE_ARGS
 
-      - name: install-sass
-        run: |
-          npm install -g sass
+      - uses: dw-labs-org/dart-sass-gha@v1
 
       - name: build-frontend
         run: |
@@ -80,9 +78,7 @@ jobs:
         env:
           FLAVOUR: '9.10'
 
-      - name: install-sass
-        run: |
-          npm install -g sass
+      - uses: dw-labs-org/dart-sass-gha@v1
 
       - name: build-frontend
         run: |

README.md

@@ -46,11 +46,12 @@ You can set up the toolchain by either:
 - Using [`ghcup`](https://www.haskell.org/ghcup/guide/#cross-support)
   to set up ghc 9.10
 
+Also install [Sass](https://sass-lang.com/install/).
+
 Then:
 
 ```sh
 source ~/.ghc-wasm/env
-npm install -g sass
 cd frontend
 ./build.sh
 ```