Bump actions/checkout from 5 to 6 (#22)

Update README to include Node.js 24 support details and requirements by @​salmanmkc in actions/checkout#2248
Persist creds to a separate file by @​ericsciple in actions/checkout#2286
v6-beta by @​ericsciple in actions/checkout#2298
update readme/changelog for v6 by @​ericsciple in actions/checkout#2311

Author: rljacob

.github/workflows/gh-pages.yml

@@ -18,7 +18,7 @@ jobs:
     if: ${{ github.event.repository.name != 'scream' }}
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
         with:
           persist-credentials: false
           show-progress: false

.github/workflows/md-linter.yml

@@ -12,7 +12,7 @@ jobs:
   linter:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
       with:
         fetch-depth: 0
     - uses: tj-actions/changed-files@v47