refactor: clean up gallery tooling and document the workflow

scripts/build.js

@@ -2,7 +2,7 @@ const fs = require("fs");
 const path = require("path");
 
 const { getRankedMeals, syncEloWithMeals } = require("./lib/elo");
-const { loadMeals, repoRoot } = require("./lib/meals");
+const { loadMeals, repoRoot, validateMealAssets } = require("./lib/meals");
 
 const indexTemplatePath = path.join(repoRoot, "templates", "index.html");
 const indexOutputPath = path.join(repoRoot, "index.html");
@@ -126,6 +126,7 @@ function replaceBlock(template, token, replacement) {
 }
 
 function buildIndex(meals = loadMeals()) {
+  validateMealAssets(meals);
   const template = fs.readFileSync(indexTemplatePath, "utf8");
   const eol = detectEol(template);
 
@@ -136,6 +137,7 @@ function buildRankings(
   meals = loadMeals(),
   eloData = syncEloWithMeals(meals)
 ) {
+  validateMealAssets(meals);
   const template = fs.readFileSync(rankingsTemplatePath, "utf8");
   const eol = detectEol(template);
   const rankedMeals = getRankedMeals(meals, eloData);