Add Hatch wheel build target to pyproject.toml

Hatchling 1.19.0 changed the package identification heuristics such that an
explicit declaration of the code directory tree to build the wheel for
installation from is now required.

pyproject.toml

@@ -76,5 +76,8 @@ source = [ "salishsea_cmd", "tests"]
 show_missing = true
 
 
+[tool.hatch.build.targets.wheel]
+packages = ["salishsea_cmd"]
+
 [tool.hatch.version]
 path = "salishsea_cmd/__about__.py"