Add paraIds to w:p elements

[christianvoigt]

Is your feature request related to a problem? Please describe.
In our app I am relying on paraIds ("w14:paraId" attributes) to identify specific w:p elements in the docx file and apply changes to them. Docx files from Word or Google Docs do contain these attributes. Docx files generated with remark-docx do not seem to have paraIds.

Describe the solution you'd like
Generate ids for each w:p element and add them as w14:paraId attributes.

Describe alternatives you've considered
Right now I have to postprocess the docx file to add the paraIds in our own code.

[lancejpollard]

@christianvoigt how do you do the postprocessing? Can you share sample code?