Fixes to #628 to help it pass typescript's type checking (#634)

* My best interpretation of what the typings should look like after merge of #464

* Apply variable name changes as per Juice10 review

Co-authored-by: Justin Halsall <Juice10@users.noreply.github.com>

* fix types

Co-authored-by: Eoghan Murray <eoghan@getthere.ie>

src/types.ts

@@ -295,9 +295,11 @@ export type textMutation = {
 };
 
 export type styleAttributeValue = {
-  [key:string]: [string, string] | string | false;
+  [key:string]: styleValueWithPriority | string | false;
 };
 
+export type styleValueWithPriority = [string, string];
+
 export type attributeCursor = {
   node: Node;
   attributes: {