feat: adding image for mastodon posts (#349)

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

## Summary by CodeRabbit

* **New Features**
* Release announcements on social channels now include a branded image
with an accessible description, improving clarity and visual presence.

* **Chores**
* Improved the release announcement automation to ensure reliable
posting.
* Refined the trigger configuration to accurately run announcements when
the changelog is updated.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Author: cmeesters

.github/workflows/announce-release.yml

@@ -4,7 +4,7 @@ on:
   push:
     branches:
       - main
-    path:
+    paths:
       - 'CHANGELOG.md'
 
 permissions:
@@ -15,11 +15,16 @@ jobs:
     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: ${{ github.event.head_commit.message }}
+          image: "${{ github.workspace }}/pr_logo/long_logo_hpc.png"
+          image-description: "Snakemake HPC logo for Mastodon"
           message: |
             Beep, Beep - I am your friendly #Snakemake release announcement bot.