Update to Node 18 (#550)

* update to Node 18 (latest LTS) and add .nvmrc for CLI instructions

* update vite to latest minor

* update github workflows to Node 18.x

---------

Co-authored-by: Mads Rasmussen <madsr@hey.com>

src/Umbraco.Web.UI.Client/.github/workflows/build_test.yml

@@ -22,7 +22,7 @@ jobs:
 
     strategy:
       matrix:
-        node-version: [16.x]
+        node-version: [18.x]
 
     steps:
     - uses: actions/checkout@v3

src/Umbraco.Web.UI.Client/.github/workflows/playwright.yml

@@ -12,7 +12,7 @@ jobs:
     - uses: actions/checkout@v3
     - uses: actions/setup-node@v3
       with:
-        node-version: '16.x'
+        node-version: '18.x'
         cache: 'npm'
     - name: Install dependencies
       run: npm ci