Add HOME=/root to container samples in docs (#27832)

Reference: #6500
(https://github.com/microsoft/playwright/issues/6500#issuecomment-1664210041)

It seems that this is now required, so this PR applies that to the docs.

Signed-off-by: Jozef Hollý <1708197+j2ghz@users.noreply.github.com>

docs/src/ci-intro.md

@@ -189,6 +189,8 @@ jobs:
         run: npm ci
       - name: Run your tests
         run: npx playwright test
+        env:
+          HOME: /root
 ```
 
 ```yml python title=".github/workflows/playwright.yml"
@@ -217,6 +219,8 @@ jobs:
           pip install -e .
       - name: Run your tests
         run: pytest
+        env:
+          HOME: /root
 ```
 
 ```yml java title=".github/workflows/playwright.yml"
@@ -242,6 +246,8 @@ jobs:
         run: mvn -B install -D skipTests --no-transfer-progress
       - name: Run tests
         run: mvn test
+        env:
+          HOME: /root
 ```
 
 ```yml csharp title=".github/workflows/playwright.yml"
@@ -266,6 +272,8 @@ jobs:
       - run: dotnet build
       - name: Run your tests
         run: dotnet test
+        env:
+          HOME: /root
 ```
 
 ### On deployment