Convert wiring AST to Brick Diagrams v1 format

[sjoerdvisscher]

todo

• Convert ASTs roughly like this one into brick diagrams.
• Add documentation (see the stuff below for example) to https://docs.statebox.org, e.g. here. Covered by Marco's 'How we store diagrams' document.
• Add one or more test to check that the resulting Statebox.Core.Types.Diagram matches the expected one.

encoding

Erik: In the brick editor we can draw the following, but is it possible to encode this using a wiring tree? (??1!)

-------------
|     a     |
-------------
|  b  |  c  | 
-------------
|     d     |
-------------

Jelle: why not? a.output_1~b.input_1 a.o2~c.i1 b.o1~d.i1 c.o1~d.i2

[sjoerdvisscher]

Documentation is perfectly covered by https://hackmd.io/0CPzJ_V-Qkm0y40NLQRhWw?view#Brick-diagrams-for-string-diagrams

[epost]

Added a bullet to add tests.