Add --version flag #378
Description
As per https://clig.dev/ we should have a --version flag on generator and other commands. This should display the linkml version - perhaps also runtime.
not sure how to implement this:
>>> import linkml
RDFLib Version: 5.0.0
>>> linkml.__version__
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
AttributeError: module 'linkml' has no attribute '__version__'