Run package-local prettier

Instead of running a single global version of prettier, which might
conflict with the package-local version that editors might be using,
we instead run prettier within each package that has it installed as a
dependency.

.github/workflows/prettier.yml

@@ -13,6 +13,24 @@ jobs:
         uses: actions/checkout@v2
       - name: Run prettier
         run: |-
-          npx prettier -c 'examples/**/*.{js,jsx,ts,tsx,css,md,json}' 
+          function run_check() {
+            if $(grep -q '"prettier"' "$1") ; then
+              pushd "$(dirname $1)"
+              echo "Running prettier on $(pwd)"
+              npx prettier -c '**/*.{js,jsx,ts,tsx,css,md,json}'
+              popd
+            fi
+          }
+          find . -type f -name 'package.json' ! -path '*node_modules*' -print0 | while IFS= read -r -d '' file; do
+            run_check "$file"
+          done
+
+  # i18n is not a node package, so we handle that one separately
+  format-i18n:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out repo
+        uses: actions/checkout@v2
+      - name: Run prettier
+        run: |-
           npx prettier -c 'i18n/**/*.{js,jsx,ts,tsx,css,md,json}'
-          npx prettier -c 'www/**/*.{js,jsx,ts,tsx,css,md,json}'