feat: add helm-chart name extraction action (#4)

Reviewed-on: #4
Co-authored-by: Timo Behrendt <t.behrendt@t00n.de>
Co-committed-by: Timo Behrendt <t.behrendt@t00n.de>

.gitea/actions/extract-chart-name-from-repo-name/action.yaml

@@ -0,0 +1,19 @@
+name: Extract chart name from repo name
+description: Extracts the chart name from the repo name, based on the convention of helm-<chart-name>
+inputs:
+  repo:
+    description: The full repository name (e.g., "helm-my-chart")
+    required: true
+outputs:
+  chart-name:
+    description: The extracted chart name
+    value: ${{ steps.extract.outputs.suffix }}
+runs:
+  using: "composite"
+  steps:
+    - id: extract
+      shell: bash
+      run: |
+        full_repo="${{ inputs.repo }}"
+        suffix="${full_repo##*helm-}" 
+        echo "suffix=$suffix" >> $GITHUB_OUTPUT