chore: replace Dependabot with custom script

Dependabot doesn't properly tidy Go dependencies across the repository
and lacks customization options. We've replaced it with a custom script
that correctly updates and tidies dependencies on a weekly schedule.

Signed-off-by: Michael Gasch <[email protected]>

Author: embano1

.github/dependabot.yml

@@ -1,10 +1,5 @@
 version: 2
 updates:
-- package-ecosystem: gomod
-  directory: "/"
-  schedule:
-    interval: daily
-  open-pull-requests-limit: 5
 - package-ecosystem: "github-actions"
   directory: "/"
   schedule:

.github/workflows/update-dependencies.yml

@@ -0,0 +1,60 @@
+name: Update Dependencies
+
+on:
+  schedule:
+    # Runs every Monday at 3:00 AM UTC
+    - cron: '0 3 * * 1'
+  # Allow manual triggering
+  workflow_dispatch:
+
+jobs:
+  update-dependencies:
+    strategy:
+      matrix:
+        go-version: [1.23]
+        platform: [ubuntu-latest]
+    runs-on: ${{ matrix.platform }}
+    permissions:
+      contents: write
+      pull-requests: write
+    
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
+
+      - name: Setup Go ${{ matrix.go-version }}
+        uses: actions/setup-go@0aaccfd150d50ccaeb58ebd88d36e91967a5f35b # v5.4.0
+        with:
+          go-version: ${{ matrix.go-version }}
+          cache-dependency-path: v2/go.sum
+        id: go
+
+      - name: Run update dependencies script
+        run: |
+          chmod +x ./hack/update-deps.sh
+          ./hack/update-deps.sh
+
+      - name: Check for changes
+        id: check-changes
+        run: |
+          if [[ -n "$(git status --porcelain '**/go.mod' '**/go.sum')" ]]; then
+            echo "changes=true" >> $GITHUB_OUTPUT
+          else
+            echo "changes=false" >> $GITHUB_OUTPUT
+          fi
+
+      - name: Create Pull Request
+        if: steps.check-changes.outputs.changes == 'true'
+        uses: peter-evans/create-pull-request@271a8d0340265f705b14b6d32b9829c1cb33d45e
+        with:
+          token: ${{ secrets.GITHUB_TOKEN }}
+          commit-message: "chore: update dependencies"
+          title: "chore: update dependencies"
+          body: |
+            This PR updates Go dependencies.
+            
+            This is an automated PR created by the weekly dependency update workflow.
+          branch: automated-dependency-updates
+          delete-branch: true
+          labels: deps,chore
+          reviewers: sdk-go-maintainers

README.md

@@ -20,7 +20,7 @@ This library will help you to:
 _Note:_ Supported
 [CloudEvents specification](https://github.com/cloudevents/spec): 0.3, 1.0
 
-_Note:_ Supported go version: 1.22+
+_Note:_ Tested and supported go version(s): 1.23+
 
 ## Get started