feat: add the RetroBIOS PortMaster port

ports/RetroBIOS runs install.py on a handheld with PortMaster's own
screens (pugwash fifo_control through PortMasterDialog.txt), using only
what PortMaster 2024.02.26 and the 8.5.23 copy JELOS ships. It reads the
installer through --events. scripts/build_port.py writes RetroBIOS.zip
in the layout PortMaster's release build gives a port, with the
install.py the bootstraps pin, reproducibly. tests/test_port drives the
screens with stubbed dialog functions and a fake installer.

.github/workflows/validate.yml

@@ -17,6 +17,8 @@ on:
       - "install.py"
       - "install.sh"
       - "install.ps1"
+      # The handheld port bundles install.py and its tests read both.
+      - "ports/**"
       # Every input of the site build, so a page that would fail the deploy
       # fails here first (tests/test_workflow_paths.py).
       - "wiki/**"
@@ -42,6 +44,7 @@ on:
       - "install.py"
       - "install.sh"
       - "install.ps1"
+      - "ports/**"
       - "wiki/**"
       - "docs_assets/**"
       - "provenance/**"