feat: added announcement robot (#109)

added the mastodon announcement bot to snakedeploy. 

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **Chores**
* Added automated Mastodon release announcements triggered by release
commits on main.
* Publishes a standardized, multi-paragraph post including version,
extracted release notes, links to changelog and release pages, and an
attached image with description.
* Uses a secure project token to publish posts and runs as part of the
main-branch release workflow for consistent, timely announcements.

<sub>✏️ Tip: You can customize this high-level summary in your review
settings.</sub>
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

---------

Co-authored-by: Johannes Köster <[email protected]>

Author: cmeesters

.github/workflows/announce-release.yml

@@ -0,0 +1,43 @@
+name: Announce Release on Mastodon
+
+on:
+  push:
+    branches:
+      - main
+    paths:
+      - 'CHANGELOG.md'
+
+permissions:
+  pull-requests: read
+
+jobs:
+  post_to_mastodon:
+    if: "${{ contains(github.event.head_commit.message, 'chore(main): release') }}"
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+      
+      - name: Post to Mastodon
+        uses: snakemake/mastodon-release-post-action@main # == latest
+        with:
+          access-token: ${{ secrets.MASTODONBOT }}
+          pr-title: ${{ github.event.head_commit.message }}
+          image: "snakedeploy_transparent.png"          
+          image-description: "Snakedeploy logo - altered for Mastodon"
+          message: |
+            Beep, Beep - I am your friendly #Snakemake release announcement bot.
+            
+            There is a new release of the Snakedeploy tool to deploy Snakemake workflows from the snakemake catalog. Its version now is {{ version }}!
+            
+            Give us some time, and you will automatically find Snakedeploy on #Bioconda and #Pypi.
+            
+            If you want to discuss the release, you will find the maintainers here on Mastodon!
+            @[email protected]
+            
+            If you discover any issues, please report them on {{ issue_url }}.
+
+            See {{ changelog }} for details. Here is the header of the changelog:
+            
+            ${{ steps.extract-release-notes.outputs.release_notes }}
+