chore(doc): Add a change log.

And fix an typo.

Signed-off-by: cryptcoin-junkey <cryptcoin.junkey@gmail.com>

doc/release-notes-monacoin.md

@@ -82,7 +82,7 @@ new scrypt.c from Verge
 -----------------------
 
 scrypt.c is replaced from Litecoin's to Verge's.
-New scrypt.c is OPenSSL free. And it is enough stable.
+New scrypt.c is OpenSSL free. And it is enough stable.
 Note that it is not lisensed under MITL. Please see the license
 header in `src/crypto/scrypt.cpp`.
 
@@ -95,6 +95,13 @@ Some people think risks of rewind attacks by crackers.
 But no worry. The recent Monacoin chain has enough hash power.
 Thanks miners for keeping work.
 
+0.20.3 change log
+=================
+
+### Miscellaneous
+
+- #101 Fix the invalid value in MESSAGE_MAGIC
+
 Credits
 =======