Include "tests" folders in the build tool groups

Allow absent "prefix" in group entries to simplify the code

src/wireviz/tools/build_examples.py

@@ -31,6 +31,7 @@
  "path": dir / "examples",
  "prefix": "demo",
  },
+ **{p.stem: {"path": p} for p in (dir / "tests").glob("**")},
 }
 
 input_extensions = [".yml"]
@@ -43,7 +44,7 @@
 
 def collect_filenames(description, groupkey, ext_list):
  path = groups[groupkey]["path"]
- patterns = [f"{groups[groupkey]['prefix']}*{ext}" for ext in ext_list]
+ patterns = [f"{groups[groupkey].get('prefix', '')}*{ext}" for ext in ext_list]
  if ext_list != input_extensions and readme in groups[groupkey]:
  patterns.append(readme)
  print(f'{description} {groupkey} in "{path}"')