Allow nodes to be constructed #96
Description
Feature Use Case
PostCSS provides top-level functions (postcss.rule() et al) for creating new nodes from scratch. This is particularly useful in conjunction with Node.replaceWith() when a processor makes edits to a stylesheet. It would be similarly useful to be able to construct new value-level nodes.
Feature Proposal
To match the PostCSS API, export functions that construct all the value datatypes, like word() and string() and so on.