doc/assy: add constraints

[marcus7070]

Will resolve #715.

This is still a WIP, but it's mostly done and I won't be able to get back to it for a few days, so I figured I'd open this draft PR incase anyone wants to check it out.

Still to do:

• Consider a more gentle introduction to constraints (Why you would use them? Define what I mean when I say first object, second object?)
• Introduce dummy geometry Introduce dummy Shapes in the assembly docs #856
• Run my code examples through black
• Is that Plane 3D example really worth it? Should I just replace it with a 3 line code block?
• Explain why rotation has to be locked with PointInPlane, but you can get away without doing it for just Point Not going to add this, it reads better without it
• Consider applying better formatting to the list of colors (flexbox or something?)
• Docstring at the top of gen_colors.py, it's not obvious what it's used for
• Explain initial locations

[Jojain]

It could be nice to have a note that says something like :

• Since solve() is computing an optimization, it is sensible to initials parameters. Thus having your shapes positioned roughly were you want them to be can give better results/ make the assembly converge. Especially if all your parts are overlapping at the beginning.

(I am not 100% sure this is true though lol)

[marcus7070]

• Since solve() is computing an optimization, it is sensible to initials parameters. Thus having your shapes positioned roughly were you want them to be can give better results/ make the assembly converge. Especially if all your parts are overlapping at the beginning.

Thanks @Jojain. Yeah, I won't word it exactly like that (I think no initial locations is fine for the majority of uses), but if I'm explaining how constraints work then I should also explain initial locations as well.

[jmwright]

@marcus7070 Still seeing the following black error in CI.

would reformat doc\conf.py
Oh no! \U0001f4a5 \U0001f494 \U0001f4a5
1 file would be reformatted, 67 files would be left unchanged.
Command exited with code 1

[jmwright]

LGTM, thanks @marcus7070 !

[adam-urbanczyk]

Great, looks good! Just one more black run and all should be green.

[marcus7070]

@marcus7070 Still seeing the following black error in CI.

would reformat doc\conf.py
Oh no! \U0001f4a5 \U0001f494 \U0001f4a5
1 file would be reformatted, 67 files would be left unchanged.
Command exited with code 1

Thanks, I just had to add a comma to a list. Assuming this all passes I'll merge in a few minutes.

[marcus7070]

Just a leftover error because this branch doesn't contain #872, so I'll merge.