Open "about" paragraph by default

Fixes #36.

package.json

@@ -1,6 +1,6 @@
 {
     "name": "interlanguage-checker",
-    "version": "1.10.15",
+    "version": "1.10.16",
     "description": "Check the consistency of MediaWiki interlanguage links in a simple overview.",
     "author": "Felix W. Dekker",
     "browser": "dist/bundle.js",

src/main/index.html

@@ -32,7 +32,7 @@
         <section class="container">
             <div class="row">
                 <div class="column">
-                    <details>
+                    <details open id="about">
                         <summary><b>About</b></summary>
                         <span>
                         <a href="https://community.fandom.com/wiki/Help:Interlanguage_link">Interlanguage links</a>

src/main/js/Main.js

@@ -23,6 +23,16 @@ doAfterLoad(() => {
     $("main").style.display = null;
 });
 
+doAfterLoad(() => {
+    const about = $("#about");
+    const key = "/tools/interlanguage-checker//toggle-about";
+
+    about.addEventListener("toggle", () => localStorage.setItem(key, "" + !!about.open));
+
+    const storedState = localStorage.getItem(key);
+    if (storedState === null) about.open = true;
+    else about.open = storedState === "true";
+});
 
 doAfterLoad(async () => {
     const urlInput = new ValidatableInput($("#url"), (value) => {