Update actions/{cache,checkout,upload-artifact} (#29)

* Update `actions/cache` and `actions/checkout`

* Update `actions/upload-artifacts`

* Create dependabot.yml

---------

Co-authored-by: Morten Piibeleht <morten.piibeleht@gmail.com>

Author: barucden

.github/dependabot.yml

@@ -0,0 +1,7 @@
+# https://docs.github.com/github/administering-a-repository/configuration-options-for-dependency-updates
+version: 2
+updates:
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "weekly"

.github/workflows/PDFs.yml

@@ -23,12 +23,12 @@ jobs:
       JULIA_SOURCE: ${{ github.workspace }}/pdf/build/julia
       JULIA_DOCS: ${{ github.workspace }}/pdf/build/docs.julialang.org
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - uses: julia-actions/setup-julia@v1
         with:
           version: 1
           show-versioninfo: true
-      - uses: actions/cache@v1
+      - uses: actions/cache@v4
         env:
           cache-name: cache-artifacts
         with:
@@ -45,7 +45,7 @@ jobs:
       - run: julia --color=yes pdf/make.jl ${{ matrix.buildtype }}
         env:
           DOCUMENTER_LATEX_DEBUG: ${{ github.workspace }}/latex-debug-logs
-      - uses: actions/upload-artifact@v3
+      - uses: actions/upload-artifact@v4
         if: ${{ always() }}
         with:
           name: "LaTeX source and logs (${{ matrix.buildtype }})"