fix(ci): cache ipfs-webui

This should stabilize CI by reducing the umber of times we fetch the
same version of ipfs-webui.

.github/workflows/ci.yml

@@ -8,8 +8,52 @@ env:
 
 jobs:
 
+  webui:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out Git repository
+        uses: actions/checkout@v2
+
+      - name: Install Node.js
+        uses: actions/setup-node@v2
+        with:
+          node-version: 'lts/*'
+
+      - name: Cache webui
+        uses: actions/cache@v2
+        id: webui-cache
+        with:
+          path: assets/webui
+          key: ${{ hashFiles('package.json') }} # webui CID is defined in this file
+
+      - name: Cache bigger downloads
+        uses: actions/cache@v2
+        id: cache
+        if: steps.webui-cache.outputs.cache-hit != 'true'
+        with:
+          path: ${{ github.workspace }}/.cache
+          key: ${{ runner.os }}-${{ hashFiles('package.json', 'package-lock.json', 'electron-builder.yml') }}
+          restore-keys: |
+            ${{ runner.os }}-${{ hashFiles('package.json', 'package-lock.json', 'electron-builder.yml') }}
+            ${{ runner.os }}-
+
+      - name: Install dependencies and fetch ipfs-webui
+        if: steps.webui-cache.outputs.cache-hit != 'true'
+        run: |
+          npm ci --prefer-offline --no-audit --progress=false --cache ${{ github.workspace }}/.cache/npm
+          npm run clean
+          npm run build:webui
+
+      - name: Attach cached ipfs-webui to Github Action
+        uses: actions/upload-artifact@v2
+        with:
+          name: ipfs-webui
+          path: assets/webui
+          if-no-files-found: error
+
   test:
     runs-on: ${{ matrix.os }}
+    needs: webui
     strategy:
       fail-fast: false
       matrix:
@@ -22,7 +66,14 @@ jobs:
       - name: Install Node.js
         uses: actions/setup-node@v2
         with:
-          node-version: '14'
+          node-version: 'lts/*'
+
+      - name: Cache webui
+        uses: actions/cache@v2
+        id: webui-cache
+        with:
+          path: assets/webui
+          key: ${{ hashFiles('package.json') }}
 
       - name: Cache bigger downloads
         uses: actions/cache@v2