docs: Show as badge in readme original openDTU release number

Badge shows the openDTU release which is used as core to build openDTU-onBattery's release

.github/workflows/build.yml

@@ -118,6 +118,23 @@ jobs:
     steps:
       - name: Checkout
         uses: actions/checkout@v3
+      
+      - name: Get tags
+        run: git fetch --force --tags origin
+
+      - name: Get openDTU core release
+        run: |
+          echo "OPEN_DTU_CORE_RELEASE=$(git show-ref | grep 'refs/tags/v' | tail -1 | sed 's#.*/##')" >> $GITHUB_ENV
+      
+      - name: Create openDTU-core-release-Badge
+        uses: schneegans/dynamic-badges-action@v1.6.0
+        with:
+          auth: ${{ secrets.GIST_SECRET }}
+          gistID: 68b47cc8c8994d04ab3a4fa9d8aee5e6
+          filename: openDTUcoreRelease.json
+          label: based on original OpenDTU
+          message: ${{ env.OPEN_DTU_CORE_RELEASE }}
+          color: lightblue
 
       - name: Build Changelog
         id: github_release

README.md

@@ -2,7 +2,7 @@
 
 This is a fork from the Hoymiles project OpenDTU.
 
-![GitHub tag (latest SemVer)](https://img.shields.io/github/v/tag/helgeerbe/OpenDTU?label=based%20on%20original%20OpenDTU)
+![GitHub tag (latest SemVer)](https://img.shields.io/endpoint?url=https://gist.githubusercontent.com/helgeerbe/68b47cc8c8994d04ab3a4fa9d8aee5e6/raw/openDTUcoreRelease.json)
 
 <mark>This README is kept similar to the openDTU project for process reasons.</mark>
 

README_onBattery.md

@@ -2,7 +2,7 @@
 
 This is a fork from the Hoymiles project [OpenDTU](https://github.com/tbnobody/OpenDTU). This project is still under development but is being used on a day to day basis as well.
 
-![GitHub tag (latest SemVer)](https://img.shields.io/github/v/tag/helgeerbe/OpenDTU?label=based%20on%20original%20OpenDTU)
+![GitHub tag (latest SemVer)](https://img.shields.io/endpoint?url=https://gist.githubusercontent.com/helgeerbe/68b47cc8c8994d04ab3a4fa9d8aee5e6/raw/openDTUcoreRelease.json)
 
 ## Features