fix(calamares): add zsh to Default group, add minimal KDE entry (pkgrel 3)

zsh fixes the login lockout reported by jtadlock91 in Antergos-NeXT/antergos-iso#17 -
users.conf forces /bin/zsh but nothing installed it. Also add KDE Plasma (Minimal)
for low-end hardware and fix missing cosmic-greeter-dinit in the packaged COSMIC entry.

packages/calamares-branding-antergos-next/packagechooser_de.conf

@@ -47,6 +47,21 @@ items:
           - kwin-zones
           - oh-my-posh-bin
           - pacseek
+    - id: PlasmaMinimal
+      name: "KDE Plasma (Minimal)"
+      description: "Stock Plasma on Wayland — kitty, pcmanfm-qt, featherpad, grim. No branding. For low-end hardware."
+      screenshot: ""
+      netinstall:
+        name: "KDE Plasma (Minimal)"
+        selected: true
+        critical: false
+        packages:
+          - plasma-meta
+          - kitty
+          - pcmanfm-qt
+          - featherpad
+          - grim
+          - slurp
     - id: Xfce
       name: "Xfce"
       description: "Lightweight traditional desktop. Fast and low on resources."
@@ -143,3 +158,4 @@ items:
         critical: false
         packages:
           - cosmic
+          - cosmic-greeter-dinit