Added grandprimevelte to list

Added grandprimevelte to the list, but marked it as `untested`.

Author: MagicLike

README.md

@@ -76,6 +76,7 @@ Samsung | Galaxy J7 2015 | j7elte | | tested
 Samsung | Galaxy A3 2017 | a3y17lte | SM-A320FL | tested
 Samsung | Galaxy A5 2016 | [a5xelte](https://wiki.lineageos.org/devices/a5xelte) | SM-A510F | tested
 Samsung | Galaxy A7 2016 | a7xelte | | tested
+Samsung | Galaxy Grand Prime VE | grandprimevelte | SM-G531F | untested
 Samsung | Galaxy S III Neo | s3ve3g | GT-I9301I | tested
 Samsung | Galaxy S4 Mini LTE| [serranoltexx](https://wiki.lineageos.org/devices/serranoltexx) | | tested
 Samsung | Galaxy S6 | [zerofltexx](https://wiki.lineageos.org/devices/zerofltexx) | | tested