function importDeclaration( node ) {
		debug( 'Found an `import` declaration: %s', node.source.value );
		if ( node.source.type === 'Literal' ) {
			debug( '`import` literal: %s', node.source.value );
			results.literals.push( node.source.value );
		}
		// NOTE: expressions are not currently supported in `import` declarations.
	}
Callback invoked upon visiting an `ImportDeclaration` AST node.

@private
@param {Node} node - AST node
@param {*} state - start state
@param {Callback} clbk - callback to continue walking a sub-node