docs: remove superflous "be" in readme (#166)

README.md

@@ -140,7 +140,7 @@ const YourComponent = (props) => {
 
 ### `marks`
 
-Object of React components that renders different types of marks that might appear in spans. Marks can be either be simple "decorators" (eg emphasis, underline, italic) or full "annotations" which include associated data (eg links, references, descriptions).
+Object of React components that renders different types of marks that might appear in spans. Marks can either be simple "decorators" (eg emphasis, underline, italic) or full "annotations" which include associated data (eg links, references, descriptions).
 
 If the mark is a decorator, the component will receive a `markType` prop which has the name of the decorator (eg `em`). If the mark is an annotation, it will receive both a `markType` with the associated `_type` property (eg `link`), and a `value` property with an object holding the data for this mark.