chore(gh): weekly release (#892)

Signed-off-by: Dario Tranchitella <dario@tranchitella.eu>

.github/release-template.md

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+This edge release can be pulled from Docker Hub as follows:
+
+```
+docker pull clastix/kamaji:$TAG
+```
+
+> As from the v1.0.0 release, CLASTIX no longer provides stable release artefacts.
+>
+> Stable release artefacts are offered on a subscription basis by CLASTIX, the main Kamaji project contributor.
+> Learn more from CLASTIX's [Support](https://clastix.io/support/) section.

.github/workflows/release.yml

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+name: Weekly Edge Release
+
+on:
+  schedule:
+    - cron: '0 7 * * 1'  # Every Monday at 9 AM CET
+  workflow_dispatch:
+
+permissions:
+  contents: write
+
+jobs:
+  release:
+    runs-on: ubuntu-22.04
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+      - name: generating date metadata
+        id: date
+        run: |
+          CURRENT_DATE=$(date -u +'%Y-%m-%d')
+          YY=$(date -u +'%y')
+          M=$(date -u +'%_m' | sed 's/ //g')
+          FIRST_OF_MONTH=$(date -u -d "$CURRENT_DATE" +%Y-%m-01)
+          WEEK_NUM=$(( (($(date -u +%s) - $(date -u -d "$FIRST_OF_MONTH" +%s)) / 86400 + $(date -u -d "$FIRST_OF_MONTH" +%u) - 1) / 7 + 1 ))
+
+          echo "yy=$YY" >> $GITHUB_OUTPUT
+          echo "month=$M" >> $GITHUB_OUTPUT
+          echo "week=$WEEK_NUM" >> $GITHUB_OUTPUT
+          echo "date=$CURRENT_DATE" >> $GITHUB_OUTPUT
+      - name: generating tag metadata
+        id: tag
+        run: |
+          TAG="edge-${{ steps.date.outputs.yy }}.${{ steps.date.outputs.month }}.${{ steps.date.outputs.week }}"
+          echo "tag=$TAG" >> $GITHUB_OUTPUT
+      - name: generate release notes from template
+        run: |
+          export TAG="${{ steps.tag.outputs.tag }}"
+          envsubst < .github/release-template.md > release-notes.md
+      - name: create GitHub release
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: |
+          gh release create "${{ steps.tag.outputs.tag }}" \
+            --title "${{ steps.tag.outputs.tag }}" \
+            --notes-file release-notes.md