Describe the feature you'd like
Currently there is a single low-level constructor for AtomArrangements, which creates an empty atom arrangement object, after which its add method can be used to add atoms.

Use cases of condensed matter physics often require specifying atom arrangements with regular structure, such as square, triangle, honeycomb lattices. To specify these lattices, currently one need to explicitly program the coordinates of each atom in lattice. It would be much better to be able to use pre-packaged factory methods to create these arrangements, and maybe even the most general 2-d decorated Bravais lattice too.

A good reference on decorated Bravais lattices: https://courses.physics.illinois.edu/phys560/sp2011/lecture/Phys560Notes-3.pdf

How would this feature be used? Please describe.
Atom arrangements could be defined by defining a regular lattice structure and a canvas where the actual sites are placed.

1. Square lattice

   canvas_boundary_points = [(0,0), (7.5e-5, 0), (0, 7.6e-5), (7.5e-5, 7.6e-5)]
   canvas = Canvas(canvas_boundary_points)
   d = 4e-6
   register = AtomArrangement.from_square_lattice(d, canvas)

2. Rectangular lattice

   dx = 4e-6
   dy = 6e-6
   register = AtomArrangement.from_rectangular_lattice(dx, dy, canvas)

3. Honeycomb lattice

   d = 6e-6
   register = AtomArrangement.from_honeycomb_lattice(d, canvas)

4. Bravais lattice

   a1 = (0, 5e-6)
   a2 = (3e-6, 4e-6)
   register = AtomArrangement.from_bravais_lattice(a1, a2, canvas)

5. Decorated Bravais lattice

   a1 = (0, 10e-6)
   a2 = (6e-6, 8e-6)
   basis = [(0,0), (0, 5e-6), (4e-6, 2e-6)]
   register = AtomArrangement.from_bravais_lattice(a1, a2, canvas, basis=basis)

Describe alternatives you've considered
One alternative to the API from_bravais_lattice method above would be to provide n1, n2 repetition numbers of the unit cell instead of the Canvas object. This would however not allow us to fit the atom arrangement into a pre-defined bounding box, and would not allow us to create staggered arrangements, where say row 1 contains unit cells 0,1,2,3, and row 2 contains unit cells 1,2,3,4, and row 3 contains unit cells 2,3,4,5.

Additional context
Useful links:

• https://en.wikipedia.org/wiki/Bravais_lattice
• https://courses.physics.illinois.edu/phys560/sp2011/lecture/Phys560Notes-3.pdf
• https://en.wikipedia.org/wiki/Point_in_polygon