Rename abstract `text` interface to `literal`

[wooorm]

The abstract text interface (nodes with a value) interferes with the type: "text" node provided by hast and mdast (and the type: "TextNode" provided by nlcst).

Another downside is that text implies (and specifies) string values on the value field.
Say unist was used for programming values, the value of value could be specified as number, for example.

I’m open to other names, but I’m searching for something close to “raw”, “leaf”, and whatnot.

/CC @ChristianMurphy What do you think?

[ChristianMurphy]

Seems like a good direction to take, replacing Text with something more flexible.
I'd lean a bit toward Literal, Raw may conflict in some configuration type languages where there are template literals and raw literals.
I know groovy-like configuration languages distinguish between "text with ${template}" and 'raw text'

[wooorm]

@ChristianMurphy Thanks, I totes agree!

Leaf was another thing I thought of, but that would prohibit the use of something that has both a value and children in the future (and a node without value or children could also be a “leaf”, as a concept).