Show warnings if code isn't indented properly

It would be great if students were advised on proper indentation in an automated fashion. It would help them get in the habit of formatting code cleanly much sooner, and help them find obvious bugs in their own code.

From our conversation over Slack, it sounds like we could infer what indentation type the code is primarily using, and enforce that everywhere in the code.

Maybe we wouldn't want to block the page from loading when indentation errors are present, but instead add a warning annotation to the line that's improperly indented.

L'issue non indica file né test; inizia individuando i punti di ingresso dell'editor per il caricamento del codice e l'annotazione delle righe. Determina come si potrebbe inferire lo stile di indentazione e come visualizzare gli avvisi senza bloccare la pagina, quindi verifica che le righe con indentazione errata vengano annotate mentre il codice valido rimanga inalterato.