save typed reply to localStorage in thread

js/babycode-editor.js

@@ -8,6 +8,24 @@
     }
   })
   
+  const inThread = () => {
+    const scheme = window.location.pathname.split("/");
+    return scheme[1] === "threads" && scheme[2] !== "create";
+  }
+  
+  ta.addEventListener("input", () => {
+    if (!inThread()) return;
+    
+    localStorage.setItem(window.location.pathname, ta.value);
+  })
+  
+  document.addEventListener("DOMContentLoaded", () => {
+    if (!inThread()) return;
+    const prevContent = localStorage.getItem(window.location.pathname);
+    if (!prevContent) return;
+    ta.value = prevContent;
+  })
+  
   const buttonBold = document.getElementById("post-editor-bold");
   const buttonItalics = document.getElementById("post-editor-italics");
   const buttonStrike = document.getElementById("post-editor-strike");