[DEWIF] fix mardown titles

rfc/0013_Duniter_Encrypted_Wallet_Import_Format.md

-# #13 Duniter Encrypted Wallet Import Format
+# RFC 13: Duniter Encrypted Wallet Import Format
 
 ```txt
 RFC: 13
@@ -29,19 +29,19 @@ Today DUBP manage only the algorithm ED25519, but in the future DUBP can evolve
 
 So currently a public key for DUBP is to be understood as an Ed25519 public key.
 
-## DEWIF format
+## DEWIF format
 
 DEWIF is an inter-operable and secure format for any DUBP wallet.
 
 DEWIF format is a base64 string.  
 This base64 string encodes a sequence of bytes whose structure is defined below.
 
-## dewif bytes structure
+## dewif bytes structure
 
 | version (4 bytes) | currency code (4 bytes) | version data (any bytes) |
 |:-----------------:|:-----------------------:|:------------------------:|
 
-## Currencies code
+## Currencies code
 
 | Currency | code       |
 |:---------|:-----------|