github: new project metadata (Sprints, etc)

[srl295]

the new projects at https://github.com/features/issues seem interesting…

• would be great to be able to get the Sprint due date out of this and use it as the Task due date
• looks like the API for it may be graphql only - see https://github.com/github/feedback/discussions/5616 and related

[Mat-moran]

It would be very nice to be able to map github projects fields into taskwarrior fields. A mapping function is going to be needed problably because Projects fields are totally configurable and columns names are user dependant.

For example you can have:

• Priority column in github projects mapped to uda.priority.values and a in order to not need to have the same values in both, a mapping fuction for each value and a deault value for not found mappings in this way github.priorityMappingValues = [urgent:H, High:H, Medium:M] and github.priorityMappingDefaultValue = M
• Tags column in github projects map to Tag column in taskwarrior.