docs(showcase): add lunixpos.com (#5169)

Author: DevAdedeji

docs/content/showcase.yml

@@ -25,6 +25,8 @@ items:
     url: https://kassebil.dk/
   - name: LearnVue
     url: https://learnvue.co/
+  - name: LunixPOS
+    url: https://lunixpos.com/
   - name: Mawrble
     url: https://mawrble.com/
   - name: Meet Sponsors