fix: paste moving the cursor to the end of the input element (#515)

* Fix pasting always putting the cursor at the end of the input element.

* Fix for when you copy a mention only (pastedData is an empty string). Try this by putting the cursor in a mention (without selecting any text) and copy, and then paste.

src/MentionsInput.js

@@ -386,6 +386,17 @@ class MentionsInput extends React.Component {
       newPlainTextValue,
       getMentions(newValue, config)
     )
+
+    // Move the cursor position to the end of the pasted data
+    const startOfMention = findStartOfMentionInPlainText(
+      value,
+      config,
+      selectionStart
+    )
+    const nextPos =
+      (startOfMention || selectionStart) +
+      getPlainText(pastedMentions || pastedData, config).length
+    this.setSelection(nextPos, nextPos)
   }
 
   saveSelectionToClipboard(event) {