Fix web support, add smoke tests

1. Fix schema content resolving when running on web
   (referencing a schema with a relative path wasn't working)
2. Add smoke tests for desktop using `@vscode/test-cli`
3. Add smoke tests for web using `@vscode/test-web`

The smoke tests are very minimal; it loads a YAML file that references a
schema using a relative path and verifies the expected diagnostics
appear.

Signed-off-by: David Thompson <davthomp@redhat.com>

Author: datho7561

.github/workflows/CI.yaml

@@ -79,3 +79,37 @@ jobs:
           path: |
             test-resources/screenshots/*.png
           retention-days: 2
+
+  Smoke-Test-Web:
+    runs-on: 'ubuntu-latest'
+    steps:
+      - uses: actions/checkout@v4
+      - name: Use Node 20
+        uses: actions/setup-node@v4
+        with:
+          node-version: 20
+      - name: Install dependencies
+        run: npm ci
+      - name: Update yaml-language-server
+        run: npm i yaml-language-server@next
+      - name: Build extension
+        run: npm run build
+      - name: Run tests on web
+        run: xvfb-run npm run smoke-test-web
+
+  Smoke-Test-Desktop:
+    runs-on: 'ubuntu-latest'
+    steps:
+      - uses: actions/checkout@v4
+      - name: Use Node 20
+        uses: actions/setup-node@v4
+        with:
+          node-version: 20
+      - name: Install dependencies
+        run: npm ci
+      - name: Update yaml-language-server
+        run: npm i yaml-language-server@next
+      - name: Build extension
+        run: npm run build
+      - name: Run tests on web
+        run: xvfb-run npm run smoke-test

.vscode-test.mjs

@@ -0,0 +1,6 @@
+import { defineConfig } from '@vscode/test-cli';
+
+export default defineConfig({
+  files: 'out/smoke-test/**/*.test.js',
+  workspaceFolder: './smoke-test/',
+});