Adds context parameter to encode and decode calls (closes #499)

[kiranandcode]

This PR updates the Encodable class

class Encodable[T, U]:
  ...
  @classmethod
  def encode(cls, vl: T, env: Mapping[str, Any]) -> U: ...

  @classmethod
  def decode(cls, vl: U, env: Mapping[str, Any]) -> T: ...

[datvo06]

Based on our discussion yesterday, would it make sense to have another operation to retrieve context instead? Like in #456 ?

[eb8680]

would it make sense to have another operation to retrieve context instead?

I'm not sure I see a use case for this. What are the circumstances where would we need the context but not have access to it as a lexical variable?

[eb8680]

Let's make the argument optional (env: Mapping[str, Any] | None = None), since a lot of the time it's not necessary.

[datvo06]

Oh, I see, understood! I will adjust #456 accordingly

[kiranandcode]

ok, gotcha, will update!