Elaborate on the encoding of witness versions

Author: sipa

bip-0173.mediawiki

@@ -227,6 +227,12 @@ program is neither 20 nor 32 bytes, the script must fail.''
 As a result of the previous rules, addresses are always between 14 and 74 characters long, and their length modulo 8 cannot be 0, 3, or 5.
 Version 0 witness addresses are always 42 or 62 characters, but implementations MUST allow the use of any version.
 
+Implementations should take special care when converting the address to a
+scriptPubkey, where witness version ''n'' is stored as ''OP_n''. OP_0 is
+encoded as 0x00, but OP_1 through OP_16 are encoded as 0x51 though 0x60
+(81 to 96 in decimal). If a bech32 address is converted to an incorrect
+scriptPubKey the result will likely be either unspendable or insecure.
+
 ===Compatibility===
 
 Only new software will be able to use these addresses, and only for