chore: sync project files to match upstream templates (#4537)

- updated some files to match the official CodeIgniter 4 skeleton.
- rebuilt package.json from a clean init and modernized metadata and formatting
- rebuilt composer.json with modernized metadata and formatting
- replaced code of conduct text with markdown
- updated Dockerfile to replace deprecated instruction

app/Views/errors/html/debug.css

@@ -101,9 +101,11 @@ p.lead {
 }
 
 .tabs {
-    list-style: none inside none;
+    list-style: none;
+    list-style-position: inside;
+    margin: 0;
     padding: 0;
-    margin: 0 0 -1px;
+    margin-bottom: -1px;
 }
 .tabs li {
     display: inline;