Add explanations of question fields

js/lib/questions/multiple-choice.tsx

@@ -5,11 +5,15 @@ import { MarkdownView } from "../components/markdown";
 import { Markdown, QuestionFields, QuestionMethods } from "./types";
 
 export interface MultipleChoicePrompt {
+  /** The text of the prompt. */
   prompt: Markdown;
+
+  /** An array of text explaining each choice. */
   choices: Markdown[];
 }
 
 export interface MultipleChoiceAnswer {
+  /** The index of the correct answer in the choices array (0-based). */
   answer: number;
 }
 

js/lib/questions/short-answer.tsx

@@ -4,10 +4,12 @@ import { MarkdownView } from "../components/markdown";
 import { Markdown, QuestionFields, QuestionMethods } from "./types";
 
 export interface ShortAnswerPrompt {
+  /** The text of the prompt. */
   prompt: Markdown;
 }
 
 export interface ShortAnswerAnswer {
+  /** The exact string that answers the question. */
   answer: string;
 }
 

js/lib/questions/tracing.tsx

@@ -6,12 +6,18 @@ import { Snippet } from "../components/snippet";
 import { QuestionFields, QuestionMethods } from "./types";
 
 export interface TracingPrompt {
+  /** The contents of the program to trace */
   program: string;
 }
 
 export interface TracingAnswer {
+  /** True if the program should pass the compiler */
   doesCompile: boolean;
+
+  /** If doesCompile=true, then the contents of stdout after running the program */
   stdout?: string;
+
+  /** If doesCompile=false, then the line number of the code causing the error */
   lineNumber?: number;
 }