Default to UTF8 when drawing text

[Nycto]

Nim strings are encoded with UTF8 by default, so this updates the drawText proc to also default to this. I also added an optional parameter in case this needs to be overridden.

[samdze]

Makes sense.
Using UTF8 here should not bring performance penalties, I suppose.

[Nycto]

Using UTF8 here should not bring performance penalties, I suppose.

It really shouldn't. And if it does, users can still manually switch back to ascii encoding.

This is also a "principal of least surprise" kind of thing -- users are going to expect UTF8 to be the default, since it's the default in Nim. When you try to use a more complicated string right now, it spits out mojibake. This is especially salient since the default Playdate font represents things like the buttons using high order unicode characters: Ⓐ Ⓑ 🟨 ⊙ 🔒 🎣 ✛ ⬆️ ➡️ ⬇️ ⬅️

[samdze]

Thank you!