Print unknown characters using microsteps

[ArchibaldBienetre]

We will likely never get a type wheel (Typenrad, = disc with Erika's character set) that has relatively new symbols, such as

• the Euro sign
• emoji

As a workaround, we could instead use Erika's microstep feature, which is already wired up, tested and working.

[sirexeclp]

€ could be printed as C and = overlay do we have a = ?

[ArchibaldBienetre]

Good point, we could use other hacks to print unknown characters.
That should be a separate issue, though, imo.

We could apply a multi-step fallback - try the character combination hack first (for EUR, Yen, ... Pound, simple Emoji?), then resort pixelwise printing as suggested here.