Provide better debugging means

This is just to assist debugging of the runners, so that
we can grab in a case needed the screen and stderr .

* there's a script t/03_debug.t.DISABLED which needs to be renamed then
* it utilises IPC::Run3
- also showing the PATH is added for both runners
- Readme amended accordingly

.github/workflows/unit_tests_ubuntu.yml

@@ -51,6 +51,8 @@ jobs:
           printf "%s\n" "----------"
           bash --version
           printf "%s\n" "----------"
+          echo $PATH
+          printf "%s\n" "----------"
 
       - name: Install perl modules
         run: |
@@ -58,6 +60,7 @@ jobs:
           cpanm --notest Data::Dumper
           cpanm --notest JSON
           cpanm --notest Text::Diff
+          cpanm --notest IPC::Run3
 
       - name: run it
         run: |