Evaluates code in a context of a new read transaction
Output stack: result of
PumpkinDB> ["hi" RETR] READ
Will allocate for
code appended with an internal transaction end
EmptyStack error if stack is less than one item on the stack.
DatabaseError error if there's a problem with underlying storage.
Decoding error error if the code is undecodable.
evals :  READ. invalid_code : [1 READ] TRY UNWRAP 0x05 EQUAL?. empty_stack : [READ] TRY UNWRAP 0x04 EQUAL?.