[Feature Request] Support encode string for decimal

[MaryGao]

The discussion is from JS decimal support, for decimal type in typespec not every language has the native support or has the ability to handle any precision either calculation or serialization/deserialization.

So if the service team strongly cares about the precision of decimal it should use @encode to encode it as a string.

Here is the draft proposal:

model Widget {
  @encode("decimalString") // ???
  value: decimal;
}

/cc @bterlson @timotheeguerin

[markcowl]

note:

@encode(string)
myValue: decimal

[markcowl]

Closing as fixed