Social media/linkedin: add the Munich chapter logo and banner

.gitignore

@@ -2,3 +2,5 @@
 .jekyll-cache/
 
 _site/
+
+.DS_Store

_pages/muc/index.md

@@ -9,6 +9,9 @@ _**Better Software - Better Research, also in Munich!**_
 
 Our group is the place to meet other [research software engineers](https://de-rse.org/en/) in Munich. Do you write code for research? It doesn't matter if you just started or you are already an expert - This is your crowd!
 
+<img src="social_media/linkedIn/linkedIn-logo.png" alt="Logo of the Munich chapter" style="width:220px; max-width:100%; height:auto;" />
+_Munich Chapter logo._
+
 We aim for a meeting every two months, followed by dinner and networking.
 Our meetings include short talks about anything related to RSE (research data management, software development, teaching/training, and more), as well as open discussions on topics brought into the agenda by any attendee.
 

_pages/muc/social_media/linkedIn/README.md

@@ -0,0 +1,7 @@
+The logo and the banner are used since 21.03.2026 at the LinkedIn webpage of the de-RSE Munich chapter.
+https://www.linkedin.com/company/de-rse-munich-chapter
+
+Author of the banner, logo: Christina Maria Mayr -> feel free to use them (CC0)
+Christina Mayr checked that the banner is not in conflict with existing figures.
+
+