Expand `String.prototype.chars` goody test to consider strings with emojis

This task is to update [`workspaces/adventure-pack/goodies/typescript/String.prototype.chars/index.test.ts`](../tree/main/workspaces/adventure-pack/goodies/typescript/String.prototype.chars/index.test.ts) to consider a wider range of strings. In particular, it would be nice to confirm that emojis, or other strings containing Unicode characters, are correctly handled.