HMSG example is missing required sid

[bengsparks]

The shorter HMSG example is seemingly incorrect.

The specified syntax is:
HMSG <subject> <sid> [reply-to] <#header bytes> <#total bytes>␍␊[headers]␍␊␍␊[payload]␍␊

When matching against the shorter example
HMSG FOO.BAR 34 45␍␊NATS/1.0␍␊FoodGroup: vegetable␍␊␍␊Hello World␍␊,
note that only the HMSG prefix and 3 values occur before the first ␍␊ marker, despite 4 values being the minimum required by the aforementioned syntax.

The following substitutions occur
<subject> := FOO.BAR
[reply-to] := <optional>
<#header bytes> := 34
<#total bytes> := 45

which leaves sid without a value despite being required.

Changing this example to
HMSG FOO.BAR BAZ.69 34 45␍␊NATS/1.0␍␊FoodGroup: vegetable␍␊␍␊Hello World␍␊
by inserting BAZ.69, would be an appropriate and simple fix.