Replace nbsp with regular sp when extracting text

The nbsp are used by the browser to stop HTML white space collapsing
from applying, but we don't want them in the plain text version.

source/range/Contents.ts

@@ -53,6 +53,9 @@ const getTextContentsOfRange = (range: Range) => {
         }
         node = walker.nextNode();
     }
+    // Replace nbsp with regular space;
+    // eslint-disable-next-line no-irregular-whitespace
+    textContent = textContent.replace(/ /g, ' ');
 
     return textContent;
 };