Implemented Electrum mnemonic feature

how-to-create-encrypted-paper-backup/validate-bip39-mnemonic.py

@@ -0,0 +1,12 @@
+from sys import exit, stdin
+from mnemonic import Mnemonic
+
+mnemo = Mnemonic("english")
+
+lines = stdin.readlines()
+
+for line in lines:
+  if not mnemo.check(line):
+    exit(1)
+
+exit(0)