Update nuspec file to include python library

[Tom-Kingstone]

Description:

similar to LadybugTools_Toolkit, will need to include the python files as content files:

<file src="C:\ProgramData\BHoM\Extensions\PythonCode\Python_Toolkit\src\python_toolkit\bhom\wrapped\**\*.*" exclude="**\__pycache__\*;**\docs\**\*" target="contentFiles\any\any\PythonCode\Python_Toolkit\src\python_toolkit\bhom\wrapped"/>
<file src="C:\ProgramData\BHoM\Extensions\PythonCode\Python_Toolkit\src\**\*.*" exclude="**\__pycache__\*;**\docs\**\*" target="contentFiles\any\any\PythonEnvironment\Lib\site-packages" />