Add permission to right click sign editor

docs/source/permissions.rst

@@ -41,3 +41,7 @@ need to be granted the permissions you want them to have using a permissions plu
 * **purpur.place.spawners**
     - **description**: Players with this permission can place down a spawner cage and
     have the mob type restored to what it was when it was mined using silk touch.
+
+* **purpur.sign.click.opens.editor**
+    - **description**: Allows players to open the sign editor when right clicking a sign
+    while holding a sign.