first commit

show-error.mjs

@@ -0,0 +1,21 @@
+export default fetch('/error.txt').then(r=>{
+    if(r.ok) {
+        return r.text();
+    } else {
+        throw('');
+    }
+}).then(text => {
+    if(!text) {
+        return false;
+    }
+    document.body.innerHTML = '';
+    const error_show = document.createElement('pre');
+    error_show.setAttribute('id','build-error');
+    error_show.style.background = 'black';
+    error_show.style.color = 'white';
+    error_show.style.padding = '1em';
+    error_show.style['font-size'] = '16px';
+    error_show.textContent = text;
+    document.body.appendChild(error_show);
+    return true;
+}).catch(e => false);