chore: Add .node-version file and update workflows to use it

Author: baruchiro

.github/workflows/main.yml

@@ -19,7 +19,7 @@ jobs:
 
       - uses: actions/setup-node@v4
         with:
-          node-version: 18
+          node-version-file: .node-version
           cache: npm
 
       # Working around https://github.com/npm/cli/issues/4828
@@ -50,7 +50,7 @@ jobs:
       - uses: actions/checkout@v4
       - uses: actions/setup-node@v4
         with:
-          node-version: 18
+          node-version-file: .node-version
           cache: npm
           registry-url: "https://registry.npmjs.org"
 

.node-version

@@ -0,0 +1 @@
+22.x.x