refactor: group asset-related files

Fixes #15

website/assets/esbuild.config.js

@@ -0,0 +1,29 @@
+const esbuild = require("esbuild");
+
+let minify = false;
+let sourcemap = true;
+let watch_fs = true;
+
+if (process.env.NODE_ENV === "production") {
+    minify = true;
+    sourcemap = false;
+    watch_fs = false;
+}
+
+const watch = watch_fs && {
+    onRebuild(error) {
+        if (error) console.error("[watch] build failed", error);
+        else console.log("[watch] build finished");
+    },
+};
+console.log(watch);
+
+esbuild.build({
+    entryPoints: ["./js/app.js"],
+    outfile: "../source/build/app.js",
+    bundle: true,
+    minify: minify,
+    sourcemap: sourcemap,
+    watch: watch,
+    plugins: [],
+});