Bump CI Node version to 22

pnpm/action-setup installs the latest pnpm, which now requires Node
>= 22.13, so every job that enabled the pnpm cache died with
ERR_UNKNOWN_BUILTIN_MODULE on Node 20. GitHub also reports Node 20 as
deprecated on its runners.

Author: ndbroadbent

.github/workflows/deploy-docs.yml

@@ -38,7 +38,7 @@ jobs:
       - name: Setup Node
         uses: actions/setup-node@v4
         with:
-          node-version: '20'
+          node-version: '22'
 
       - name: Setup pnpm
         uses: pnpm/action-setup@v4
@@ -48,7 +48,7 @@ jobs:
       - name: Enable pnpm cache
         uses: actions/setup-node@v4
         with:
-          node-version: '20'
+          node-version: '22'
           cache: 'pnpm'
           cache-dependency-path: 'docs/pnpm-lock.yaml'
 

.github/workflows/test.yml

@@ -24,7 +24,7 @@ jobs:
       - name: Setup Node.js
         uses: actions/setup-node@v4
         with:
-          node-version: 20
+          node-version: 22
 
       - name: Setup pnpm
         uses: pnpm/action-setup@v4
@@ -34,7 +34,7 @@ jobs:
       - name: Enable pnpm cache
         uses: actions/setup-node@v4
         with:
-          node-version: 20
+          node-version: 22
           cache: pnpm
           cache-dependency-path: |
             pnpm-lock.yaml
@@ -107,7 +107,7 @@ jobs:
       - name: Setup Node.js (docs)
         uses: actions/setup-node@v4
         with:
-          node-version: 20
+          node-version: 22
 
       - name: Setup pnpm
         uses: pnpm/action-setup@v4
@@ -117,7 +117,7 @@ jobs:
       - name: Enable pnpm cache (docs)
         uses: actions/setup-node@v4
         with:
-          node-version: 20
+          node-version: 22
           cache: pnpm
           cache-dependency-path: docs/pnpm-lock.yaml