Allow setting the color of the most-left nodes

[JonasDoesThings]

Currently, you can set the color of a target node with the syntax a [10] b [red] (see demo). But there is no way of changing the color of nodes without any input-links.

We need to extend syntax for that.

Possible ways:
a) control statements, e.g.:

a [green]
a [10] b [red]

b) extended base-syntax, e.g.:

[green] a [10] b [red]

We need to decide on a syntax, and implement that.

Based on Feedback via tinyDialog:

It would be great to be able to control the color of the left most bar more precisely.

[jancborchardt]

From a user perspective, the extended base syntax seems most straightforward (option b). It’s a single line and has the color on the left, where the bar would also be.

[JonasDoesThings]

I just noticed that b) can be problematic for inputs where the labels are prefixed with a textual [sometext] deliberately. Have to think about how we can mitigate this

[jancborchardt]

Yeah, also it has to be considered whether this is actually such a big issue. There are already 3 options, them being the color of their line/bar, or black, or just hidden per the 0 width setting. Seems like that might even be enough?