This reverts commit e9298b24f212014d89fde2ddc606ac0b30b77bc8.

Client init args were changed here:
https://github.com/ziglang/zig/commit/de53e6e4f2dc7a41dc50b309fee87e06475e4838

* Fix integer overflow error

```
{
// wrong command
var stream = t.Stream.init();
stream.add("invalid data\r\n");
var client = TestClient.init(stream, config);
defer client.deinit();

try t.expectError(error.SyntaxErrorOrCommandNotFound, client.hello());
}

```

Refactor so that client can be used more easily by apps.

* Fix typo in README for `build.zig.zon` -> `build.zig`

* Fix typo in README `string` -> `smtp_client`

* Fix typo in README `Suject` -> `Subject`

Add build.zig.zon

Fix bug with SMTPUTF8