Make sure there is always some text after a link inline, so typing after a link is not impossible

schema.js

  inlines: {
    link: {
      // No link should be present but empty (default normalize should remove
      // it if this returns false).
      text: function(string) {
        return string.length !== 0
      },
        
      // If the text node after a link inline is empty...
      next: function(node) {
        return node.text.length !== 0
      },
        
      // ... then insert a space at the start of that text node.
      normalize: function(editor, {code, node}) {
        if (code === "next_sibling_invalid") {
          node.nodes.find((el, ix) => {
            const isLink = el.object === "inline" && el.type === "link"
            const next = node.nodes.get(ix + 1)
            const nextIsEmptyText = next && next.object === "text" 
                                         && next.text === ""
            
            if (isLink && nextIsEmptyText) {
                editor.insertTextByKey(next.key, 0, " ")
              
                // if the user pressed backspace we want to move the cursor
                // backwards, but if there was a selection never mind.
                const isExpanded = editor.value.selection.isExpanded
                if (!isExpanded)
                  editor.moveBackward(1)
            }
          })
        }
      }
    }
  }