Add dotted relationships arrows

[fineconstant]

Hello,

An option to make relationship arrows dotted would be very useful to express different types of relationships and distinguish them visually 😃

For now I named new elements using _Async suffix e.g. Rel_Async(...), but maybe it is better not to suggest that these new relationships are asynchronous and normal ones are synchronous... in the end it can mean something different based the context.
Other names like _Weak, _Dotted or something entirely else are possible - feel free to comment on this or suggest something 😄

[Floppy]

I like it and would definitely find it useful, but the naming would be better as _Dotted or similar, rather than adding specific semantics which aren't specified by C4.

[fineconstant]

@Floppy Thanks for feedback, I'll rename it to _Dotted as I don't have any better idea 😄

[jikuja]

Actually, Brown's book is suggesting using dashed arrows for async communications.

As with elements, you can use different line styles and colour to add an additional level of information to your diagram. For example, perhaps synchronous interactions are illustrated using solid lines, whereas asynchronous interactions are illustrated using dashed lines.

The choice of the function name is semantics and the book has another even more important point for different arrow styles:

Once again, ensure that any styling supplements the existing information wherever possible and that the styles you use are described on the key/legend.

If multiple arrow styles are used it should be easy to add description to arrows and automatically add them into legend.

[kirchsth]

@fineconstant, @Potherca: #67 is already closed, can we close this issue based on #130 too?

[fineconstant]

Close based on #130

[kirchsth]

With #160 dotted lines are supported too